Method for modulating plant growth, nucleic acid molecules and polypeptides encoded thereof useful as modulating agent

ABSTRACT

The invention provides isolated nucleic acids molecules, designated CCP nucleic acid molecules, which encode novel cell cycle associated polypeptides. The invention also provides antisense nucleic acid molecules, recombinant expression vectors containing CCP nucleic acid molecules, host cells into which the expression vectors have been introduced, and transgenic plants in which a CCP gene has been introduced or disrupted. The invention still further provides isolated CCP proteins, fusion proteins, antigenic peptides and anti-CCP antibodies. Agricultural, diagnostic, screening, and therapeutic methods utilizing compositions of the invention are also provided.

RELATED APPLICATIONS

This application claims priority to U.S. provisional patent application Ser. No. 60/204,045, filed May 12, 2000. The contents of this provisional patent application are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

Cell division plays a crucial role during all phases of plant development. The continuation of organogenesis and growth responses to a changing environment require precise spatial, temporal, and developmental regulation of cell division.

The basic mechanisms controlling the progression through the cell cycle appear to be conserved in all higher eukaryotes, although the temporal and spatial control of cell division can differ largely, between organisms. Plants have unique developmental features which are not found in either animals or fungi. First, due to the presence of a rigid cell wall, plant cells cannot move and consequently organogenesis is dependent on cell division and cell expansion at the site of formation of new organs. Secondly, cell divisions are confined to specialized regions, called meristems. These meristems continuously produce new cells which, as they move away from the meristem, become differentiated. The meristem identity itself can change from a vegetative to a reproductive phase, resulting in the formation of flowers. Thirdly, plant development is largely post-embryonic. During embryogenesis, the main developmental event is the establishment of the root-shoot axis.

Most plant growth occurs after germination, by iterative development at the meristems. Lastly, as a consequence of the sessile life of plants, development and cell division are, to a large extent, influenced by environmental factors such as light, gravity, wounding, nutrients, and stress conditions. All these features are reflected in a plant-specific regulation of the factors controlling cell division.

The unparalleled potential of plants for continuous organogenesis and plastic growth also relies on the competent or active state of the cell division apparaturs. The discovery of a common mechanism underlying the regulation of the cell cycle in yeasts and animals has led to efforts to extend these findings to the plant kingdom and is leading to research aimed at converting the gathered knowledge into useful traits introduced in transgenic plants.

When eukaryotic cells and, thus, also plant cells divide they go through a highly ordered sequence of events collectively termed as the “cell cycle.” Briefly, DNA replication or synthesis (S) and mitotic segregation of the chromosomes (M) occur with intervening gap phases (G1 and G2) and the phases follow the sequence G1-S-G2-M. Cell division is completed after cytokinesis, the last step of the M-phase. Cells that have exited the cell cycle and have become quiescent are said to be in the G0 phase. Cells at the G0 stage can be stimulated to reenter the cell cycle at the G1 phase. The transition between the different phases of the cell cycle are basically driven by the sequential activation/inactivation of a kinase (called “cyclin-dependent kinase”, “CDC” or “CDK”) by different agonists.

Proteins called cyclins are required for kinase activation. Cyclins are also important for targeting the kinase activity to a given subset of substrate(s). Other factors regulating CDK activity include CDK inhibitors (CKIs or ICKs, KIPs, CIPs, INKs), CDK activating kinase (CAK) and CDK phosphatase (CDC25) (Mironov et al. (1999) Plant Cell 11, 509-522 and Won K. et al. (1996) EMBO J. 15, 4182-4193).

SUMMARY OF THE INVENTION

The present invention is based, at least in part, on the discovery of novel plant nucleic acid molecules and polypeptides encoded by such nucleic acid molecules, referred to herein as “cell cycle proteins” or “CCP.” The CCP nucleic acid and polypeptide molecules of the present invention are useful as modulating agents in regulating cell cycle progression in, for example, plants. Accordingly, in one aspect, this invention provides isolated nucleic acid molecules encoding CCP polypeptides, as well as nucleic acid fragments suitable as primers or hybridization probes for the detection of CCP-encoding nucleic acids.

In one embodiment, a CCP nucleic acid molecule of the invention is at least 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98% or more identical to the nucleotide sequence (e.g., to the entire length of the nucleotide sequence) of SEQ ID NO:1-66 or 228-239, or a complement thereof.

In a preferred embodiment, the isolated nucleic acid molecule includes the nucleotide sequence shown in SEQ ID NO:1-66 or 228-239, or a complement thereof. In another preferred embodiment, an isolated nucleic acid molecule of the invention encodes the amino acid sequence of a plant CCP polypeptide.

Another embodiment of the invention features nucleic acid molecules, preferably CCP nucleic acid molecules, which specifically detect CCP nucleic acid molecules relative to nucleic acid molecules encoding non-CCP polypeptides. For example, in one embodiment, such a nucleic acid molecule is at least 15, 20, 25, 30, 40, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, or 800 nucleotides in length and hybridizes under stringent conditions to a nucleic acid molecule comprising the nucleotide sequence shown in SEQ ID NO:1-66\or 228-239, or a complement thereof.

In other preferred embodiments, the nucleic acid molecule encodes a naturally occurring allelic variant of a plant CCP polypeptide, wherein the nucleic acid molecule hybridizes to the nucleic acid molecule of SEQ ID NO:1-66 or 228-239 under stringent conditions.

Another embodiment of the invention provides an isolated nucleic acid molecule which is antisense to a CCP nucleic acid molecule, e.g., the coding strand of a CCP nucleic acid molecule.

Another aspect of the invention provides a vector comprising a CCP nucleic acid molecule. In certain embodiments, the vector is a recombinant expression vector. In another embodiment, the invention provides a host cell containing a vector of the invention. The invention also provides a method for producing a CCP polypeptide, by culturing in a suitable medium a host cell of the invention, e.g., a plant host cell such as a host monocot plant cell (e.g., rice, wheat or corn) or a dicot host cell (e.g., Arabidopsis thaliana, oilseed rape, or soybeans) containing a recombinant expression vector, such that the polypeptide is produced.

Another aspect of this invention features isolated or recombinant CCP polypeptides. In one embodiment, an isolated CCP polypeptides has one or more of the following domains: a “cyclin destruction box”, a “cyclin box motif 1”, a “cyclin box motif 2”, a “CDC2 motif”, a “CDK phosphorylation site”, a “nuclear localization signal”, a “Cy-like box”, an “Rb binding domain”, a “DEF domain”, a “DNA binding domain”, a “DCB1 domain”, a “DCB2 domain” and/or a “SAP domain”.

In a preferred embodiment, a CCP polypeptide includes at least one or more of the following domains: a “cyclin destruction box”, a “cyclin box motif 1”, a “cyclin box motif 2”, a “CDC2 motif”, a “CDK phosphorylation site”, a “nuclear localization signal”, a “Cy-like box”, an “Rb binding domain”, a “DEF domain”, a “DNA binding domain”, a “DCB1 domain”, a “DCB2 domain” and/or a “SAP domain”, and has an amino acid sequence at least about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, 99% or more identical to the amino acid sequence of SEQ ID NO:67-132, 205, 211, 215-216, or 220-227.

In another preferred embodiment, a CCP polypeptide includes at least one or more of the following domains: a “cyclin destruction box”, a “cyclin box motif 1”, a “cyclin box motif 2”, a “CDC2 motif”, a “CDK phosphorylation site”, a “nuclear localization signal”, a “Cy-like box”, an “Rb binding domain”, a “DEF domain”, a “DNA binding domain”, a “DCB1 domain”, a “DCB2 domain” and/or a SAP domain and has a CCP activity (as described herein).

In yet another preferred embodiment, a CCP polypeptide includes one or more of the following domains: a “cyclin destruction box”, a “cyclin box motif 1”, a “cyclin box motif 2”, a “CDC2 motif”, a “CDK phosphorylation site”, a “nuclear localization signal”, a “Cy-like box”, an “Rb binding domain”, a “DEF domain”, a “DNA binding domain”, a “DCB1 domain”, a “DCB2 domain” and/or a SAP domain and is encoded by a nucleic acid molecule having a nucleotide sequence which hybridizes under stringent hybridization conditions to a nucleic acid molecule comprising the nucleotide sequence of SEQ ID NO:1-66 or 228-239.

In another embodiment, the invention features fragments of the polypeptide having the amino acid sequence of SEQ ID NO:67-132, 205, 211, 215-216, or 220-227, wherein the fragment comprises at least 15 amino acids (e.g., contiguous amino acids) of the amino acid sequence of SEQ ID NO:67-132, 205, 211, 215-216, or 220-227. In another embodiment, a CCP polypeptide has the amino acid sequence of SEQ ID NO:67-132, 205, 211, 215-216, or 220-227.

In another embodiment, the invention features a CCP protein which is encoded by a nucleic acid molecule consisting of a nucleotide sequence at least about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, 99% or more identical to a nucleotide sequence of SEQ ID NO:1-66 or 228-239, or a complement thereof. This invention further features a CCP polypeptide, which is encoded by a nucleic acid molecule consisting of a nucleotide sequence which hybridizes under stringent hybridization conditions to a nucleic acid molecule comprising the nucleotide sequence of SEQ ID NO:1-66 or 228-239, or a complement thereof.

In another embodiment the invention provides transgenic plants (e.g., monocot or dicot plants) containing an isolated nucleic acid molecule of the present invention. For example, the invention provides transgenic plants containing a recombinant expression cassette including a plant promoter operably linked to an isolated nucleic acid molecule of the present invention. The present invention also provides transgenic seed from the transgenic plants. In another embodiment the invention provides methods of modulating, in a transgenic plant, the expression of the nucleic acids of the invention.

The proteins of the present invention or portions thereof, e.g., biologically active portions thereof, can be operatively linked to a non-CCP polypeptide (e.g., heterologous amino acid sequences) to form fusion proteins. The invention further features antibodies, such as monoclonal or polyclonal antibodies, that specifically bind polypeptide of the invention, preferably CCP polypeptide. In addition, the CCP polypeptide or biologically active portions thereof can be incorporated into pharmaceutical compositions, which optionally include pharmaceutically acceptable carriers.

In another aspect, the present invention provides a method for detecting the presence of a CCP nucleic acid molecule, polypeptide in a biological sample by contacting the biological sample with an agent capable of detecting a CCP nucleic acid molecule, polypeptide such that the presence of a CCP nucleic acid molecule, polypeptide is detected in the biological sample.

In another aspect, the present invention provides a method for detecting the presence of CCP activity in a biological sample by contacting the biological sample with an agent capable of detecting an indicator of CCP activity such that the presence of CCP activity is detected in the biological sample.

In another aspect, the invention provides a method for modulating CCP activity comprising contacting a cell capable of expressing CCP with an agent that modulates CCP activity such that CCP activity in the cell is modulated. In one embodiment, the agent inhibits CCP activity. In another embodiment, the agent stimulates CCP activity. In one embodiment, the agent is an antibody that specifically binds to a CCP polypeptide. In another embodiment, the agent modulates expression of CCP by modulating transcription of a CCP gene or translation of a CCP mRNA. In yet another embodiment, the agent is a nucleic acid molecule having a nucleotide sequence that is antisense to the coding strand of a CCP mRNA or a CCP gene.

In one embodiment, the methods of the present invention are used to increase crop yield, improve the growth characteristics of a plant (such as growth rate or size of specific tissues or organs in the plant), modify the architecture or morphology of a plant, improve tolerance to environmental stress conditions (such as drought, salt, temperature, nutrient or deprivation), or improve tolerance to plant pathogens (e.g., pathogens that abuse the cell cycle) by modulating CCP activity in a cell. In one embodiment, the CCP activity is modulated by modulating the expression of a CCP nucleic acid molecule. In yet another embodiment, the CCP activity is modulated by modulating the activity of a CCP polypeptide. Modulators of CCP activity include, for example, a CCP nucleic acid or polypeptide.

The present invention also provides diagnostic assays for identifying the presence or absence of a genetic alteration characterized by at least one of (i) aberrant modification or mutation of a gene encoding a CCP polypeptide; (ii) mis-regulation of the gene; and (iii) aberrant post-translational modification of a CCP polypeptide, wherein a wild-type form of the gene encodes a protein with a CCP activity.

In another aspect the invention provides methods for identifying a compound that binds to or modulates the activity of a CCP polypeptide, by providing an indicator composition comprising a CCP polypeptide having CCP activity, contacting the indicator composition with a test compound, and determining the effect of the test compound on CCP activity in the indicator composition to identify a compound that modulates the activity of a CCP polypeptide. The identified compounds may be used as herbicides or plant growth regulators.

Other features and advantages of the invention will be apparent from the following detailed description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP1. The complete nucleotide sequence (FIG. 1A) corresponds to nucleic acids 1 to 1715 of SEQ ID NO:39. The complete amino acid sequence (FIG. 1B) corresponds to amino acids 1 to 460 of SEQ ID NO:105. Underlined in FIG. 1A and FIG. 1B are the partially characterized nucleotide (SEQ ID NO:1) and predicted partial amino acid (SEQ ID NO:67) sequence, respectively. Further indicated in FIG. 1A are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP1 by PCR. The SEQ ID NOs of the primers used can be found in Table III. Indicated in FIG. 1B are the cyclin destruction box (black shaded box) and the cyclin box motifs 1 and 2 (both in gray shaded boxes).

FIG. 2 depicts the cDNA sequence of the Arabidopsis thaliana CCP2. The complete nucleotide sequence corresponds to nucleic acids 1 to 2195 of SEQ ID NO:40. Underlined is the partially characterized nucleotide (SEQ ID NO:2) sequence. Nucleotide sequence differences between SEQ ID NO:40 and SEQ ID NO:2 are depicted. Indicated are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP2 by PCR. SEQ ID NOs of the primers used can be found in Table III.

FIG. 3 depicts the predicted amino acid sequence of the Arabidopsis thaliana CCP2. The complete amino acid sequence corresponds to amino acids 1 to 664 of SEQ ID NO:106. Underlined is the predicted partial amino acid (SEQ ID NO:68) sequence.

FIG. 4 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP3. The complete nucleotide sequence (FIG. 3A) corresponds to nucleic acids 1 to 1413 of SEQ ID NO:41. The complete amino acid sequence (FIG. 3B) corresponds to amino acids 1 to 450 of SEQ ID NO:69. Underlined in FIG. 3A and FIG. 3B are the partially characterized nucleotide (SEQ ID NO:3) and predicted partial amino acid (SEQ ID NO:69) sequences, respectively. Indicated in FIG. 3A are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP3 by PCR. SEQ ID NOs of the primers used can be found in Table III. Nucleotide sequence differences between SEQ ID NO:41 and SEQ ID NO:3 are depicted Indicated in FIG. 3B are the cyclin destruction box (black shaded box) and the cyclin box motifs 1 and 2 (both in gray shaded boxes).

FIG. 5 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP4. The complete nucleotide sequence (FIG. 5A) corresponds to nucleic acids 1 to 672 of SEQ ID NO:4. The complete amino acid sequence (FIG. 5B) corresponds to amino acids 1 to 223 of SEQ ID NO:70. Indicated in FIG. 5A are stop and start codon (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP4 by PCR. SEQ ID NOs of the primers used can be found in Table III. Indicated in FIG. 5B is the CDK phosphorylation site to (black shaded box).

FIG. 6 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP5. The complete nucleotide sequence (FIG. 6A) corresponds to nucleic acids 1 to 1287 of SEQ ID NO:5. The complete amino acid sequence (FIG. 6B) corresponds to amino acids 1 to 429 of SEQ ID NO:71. Indicated in FIG. 6A are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP5 by PCR. SEQ ID NOs of the primers used can be found in Table III. Indicated in FIG. 6B are the cyclin destruction box (black shaded box) and the cyclin box motifs 1 and 2 (both in gray shaded boxes).

FIG. 7 depicts the cDNA sequence of the Arabidopsis thaliana CCP6. The complete nucleotide sequence corresponds to nucleic acids 1 to 2766 of SEQ ID NO:42. Underlined is the partially characterized nucleotide (SEQ ID NO:6) sequence. Indicated are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP6 by PCR. SEQ ID NOs of the primers used can be found in Table III. Nucleotide sequence differences between SEQ ID NO:42 and SEQ ID NO:6 are depicted.

FIG. 8 depicts the predicted amino acid sequence of the Arabidopsis thaliana CCP6. The complete amino acid sequence corresponds to amino acids 1 to 901 of SEQ ID NO:108. Underlined is the predicted partial amino acid (SEQ ID NO:72) sequence.

FIG. 9 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP7/CCP8. The complete nucleotide sequence (FIG. 9A) corresponds to nucleic acids 1 to 1260 of SEQ ID NO:43. The complete amino acid sequence (FIG. 9B) corresponds to amino acids 1 to 358 of SEQ ID NO:109. Underlined in FIG. 9A and FIG. 9B are the partially characterized nucleotide (SEQ ID NO:7) and predicted partial amino acid (SEQ ID NO:73) sequence, respectively. Italic sequences in FIG. 9A and FIG. 9B correspond to the partially characterized nucleotide (SEQ ID NO:8) and amino acid (SEQ ID NO:74) sequence, respectively, of another clone found independently to interact with an AtE2F protein in a yeast two-hybrid screen. Indicated in FIG. 9A are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP7/8 by PCR. SEQ ID NOs of the primers used can be found in Table III. Nucleotide sequence differences between SEQ ID NO:43 and SEQ ID NO:7-8 are depicted.

FIG. 10 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP9. The complete nucleotide sequence (FIG. 10A) corresponds to nucleic acids 1 to 1308 of SEQ ID NO:9. The complete amino acid sequence (FIG. 10B) corresponds to amino acids 1 to 436 of SEQ ID NO:75. Indicated in FIG. 10A are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP9 by PCR. SEQ ID NOs of the primers used can be found in Table III. Indicated in FIG. 10B are the cyclin destruction box (black shaded box) and the cyclin box motifs 1 and 2 (both in gray shaded boxes).

FIG. 11 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP10. The complete nucleotide sequence (FIG. 11A) corresponds to nucleic acids 1 to 1006 of SEQ ID NO:10. The complete amino acid sequence (FIG. 11B) corresponds to amino acids 1 to 254 of SEQ ID NO:76. Indicated in FIG. 11A are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP10 by PCR. SEQ ID NOs of the primers used can be found in Table III.

FIG. 12 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP11. The complete nucleotide sequence (FIG. 12A) corresponds to nucleic acids 1 to 653 of SEQ ID NO:44. Indicated in FIG. 12A are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP11 by PCR. SEQ ID NOs of the primers used can be found in Table III. However, during prediction of the open reading frame a frame shift was introduced which effected the CCP11 open reading frame. The stop codon indicated in italics in a black shaded box is the putative correct stop codon. The amino acid sequence in FIG. 12B corresponds to amino acids 1 to 86 of SEQ ID NO:77, the protein encoded by the initially identified open reading frame of SEQ ID NO:11. The putative correct complete amino acid sequence in FIG. 12C corresponds to amino acids 1 to 98 of SEQ ID NO:110.

FIG. 13 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP12/13. The complete nucleotide sequence (FIG. 13A) corresponds to nucleic acids 1 to 1266 of SEQ ID NO:45. The complete amino acid sequence (FIG. 13B) corresponds to amino acids 1 to 385 of SEQ ID NO:111. Double underlined in FIG. 13A and FIG. 13B are the partially characterized 3′ nucleotide (SEQ ID NO:12) and C-terminal predicted partial amino acid (SEQ ID NO:78) sequence, respectively. Single underlined in FIG. 13A and FIG. 13B are the partially characterized 5′ nucleotide (SEQ ID NO:13) and N-terminal predicted partial amino acid (SEQ ID NO:79) sequences, respectively. Indicated in FIG. 13A are the stop and start codons (both in black shaded boxes) and the primers (grey shaded boxes) used to amplify the coding region of CCP12/13 by PCR. SEQ ID NOs of the primers used can be found in Table III. Nucleotide sequence differences between SEQ ID NO:45 and SEQ ID NO:12 are depicted.

FIG. 14 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP14. The complete nucleotide sequence (FIG. 14A) corresponds to nucleic acids 1 to 1520 of SEQ ID NO:46. The complete amino acid sequence (FIG. 14B) corresponds to amino acids 1 to 465 of SEQ ID NO:112. Underlined in FIG. 14A and FIG. 14B are the partially characterized nucleotide (SEQ ID NO:14) and predicted partial amino acid (SEQ ID NO:80) sequence, respectively. Indicated in FIG. 14A are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP14 by PCR. SEQ ID NOs of the primers used can be found in Table III.

FIG. 15 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP15. The complete nucleotide sequence (FIG. 15A) corresponds to nucleic acids 1 to 1142 of SEQ ID NO:47. The complete amino acid sequence (FIG. 1B) corresponds to amino acids 1 to 313 of SEQ ID NO:113. Underlined in FIG. 15A and FIG. 15B are the partially characterized nucleotide (SEQ ID NO:15) and predicted partial amino acid (SEQ ID NO:81) sequence, respectively. Indicated in FIG. 15A are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP 15 by PCR. SEQ ID NOs of the primers used can be found in Table III. Nucleotide sequence differences between SEQ ID NO:47 and SEQ ID NO:15 are depicted. Indicated in FIG. 15B are the PSTTLRE motif (boxed) characteristic for the subclass of plant PSTTLRE CDC2 kinases.

Further indicated in FIG. 15B are three CDC2 motifs (black shaded box, grey shaded box and double underlined). Other residues conserved in CDC2s are underscored by ‘*’ (residues in common with Propom domain PD198850), ‘+’ (residues in common with Propom domain PD015684), (residues in common with Propom domain PD063669), and ‘1’ (residues in common with Propom domain PD195780).

FIG. 16 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP16. The complete nucleotide sequence (FIG. 16A) corresponds to nucleic acids 1 to 1189 of SEQ ID NO:48. The complete amino acid sequence (FIG. 16B) corresponds to amino acids 1 to 292 of SEQ ID NO:114. Indicated in FIG. 16A are the stop and the three possible start codons (all in black shaded boxes) and the primers (grey shaded boxes) used to amplify the coding region of CCP16 by PCR. SEQ ID NOs of the primers used can be found in Table III. Nucleotide sequence differences between SEQ ID NO:48 and SEQ ID NO:16 are depicted. Indicated in FIG. 16B are the DNA binding domain (black shaded box), DEF domain (grey shaded box), DCB1 domain (single underlined) and DCB2 domain (double underlined), all domains characteristic for a DP protein.

FIG. 17 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP17. The complete nucleotide sequence (FIG. 17A) corresponds to nucleic acids 1 to 794 of SEQ ID NO:17. The complete amino acid sequence (FIG. 17B) corresponds to amino acids 1 to 173 of SEQ ID NO:83. Indicated in FIG. 17A are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP17 by PCR. SEQ ID NOs of the primers used can be found in Table III.

FIG. 18 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP18. The complete nucleotide sequence (FIG. 18A) corresponds to nucleic acids 1 to 805 of SEQ ID NO:49. The complete amino acid sequence (FIG. 18B) corresponds to amino acids 1 to 165 of SEQ ID NO:115. Underlined in FIG. 15A and FIG. 15B are the partially characterized nucleotide (SEQ ID NO:18) and predicted partial amino acid (SEQ ID NO:84) sequence, respectively. Indicated in FIG. 18A are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP18 by PCR. SEQ ID NOs of the primers used can be found in Table III.

FIG. 19 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP19. The complete nucleotide sequence (FIG. 19A) corresponds to nucleic acids 1 to 1152 of SEQ ID NO:19. The complete amino acid sequence (FIG. 1B) corresponds to amino acids 1 to 383 of SEQ ID NO:85. Indicated in to FIG. 19A are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP19 by PCR. SEQ ID NOs of the primers used can be found in Table III.

FIG. 20 depicts the cDNA sequence of the Arabidopsis thaliana CCP20/21. The complete nucleotide sequence corresponds to nucleic acids 1 to 1539 of SEQ ID NO:50. Underlined are the partially characterized 5′ nucleotide (SEQ ID NO:20) sequence and the partially characterized 3′ nucleotide (SEQ ID NO:21). Indicated in FIG. 20 are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP20/21 by PCR. SEQ ID NOs of the primers used can be found in Table III. Nucleotide sequence differences between SEQ ID NOs:20-21 and SEQ ID NO:50 are depicted.

FIG. 21 depicts the predicted amino acid sequence of the Arabidopsis thaliana CCP20/21. The complete amino acid sequence corresponds to amino acids 1 to 432 of SEQ ID NO:116. Underlined are the partially characterized N-terminal predicted partial amino acid (SEQ ID NO:50) sequence and the partially characterized C-terminal amino predicted partial acid (SEQ ID NO: 87) sequence. Indicated are further differences in amino acid sequence between SEQ ID NO:87 and SEQ ID NO:116.

FIG. 22 depicts the cDNA sequence of the Arabidopsis thaliana CCP22. The complete nucleotide sequence corresponds to nucleic acids 1 to 1977 of SEQ ID NO:51. Underlined is the partially characterized nucleotide (SEQ ID NO:22). Indicated are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP22 by PCR. SEQ ID NOs of the primers used can be found in Table III.

FIG. 23 depicts the predicted amino acid sequence of the Arabidopsis thaliana CCP22. The complete amino acid sequence corresponds to amino acids 1 to 559 of SEQ ID NO:117. Underlined is the predicted partial amino acid (SEQ ID NO:88) sequence.

FIG. 24 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP23. The complete nucleotide sequence (FIG. 24A) corresponds to nucleic acids 1 to 525 of SEQ ID NO:52. Indicated in FIG. 24A are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP23 by PCR. SEQ ID NOs of the primers used can be found in Table III. Nucleotide sequence differences between SEQ ID NOs:23 and SEQ ID NO:52 are depicted. The amino acid sequence in FIG. 24B corresponds to amino acids 1 to 98 of SEQ ID NO:89. The complete amino acid sequence in FIG. 24C corresponds to amino acids 1 to 86 of SEQ ID NO:118.

FIG. 25 depicts the cDNA sequence of the Arabidopsis thaliana CCP24. The complete nucleotide sequence corresponds to nucleic acids 1 to 2610 of SEQ ID NO:53. Underlined is the partially characterized nucleotide (SEQ ID NO:24). Indicated are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP24 by PCR. SEQ ID NOs of the primers used can be found in Table III.

FIG. 26 depicts the predicted amino acid sequence of the Arabidopsis thaliana CCP24. The complete amino acid sequence corresponds to amino acids 1 to 784 of SEQ ID NO:119. Underlined is the predicted partial amino acid (SEQ ID NO:90) sequence.

FIG. 27 depicts the cDNA sequence of the Arabidopsis thaliana CCP25. The complete nucleotide sequence corresponds to nucleic acids 1 to 2235 of SEQ ID NO:54. Underlined is the partially characterized nucleotide (SEQ ID NO:25) sequence. Indicated are stop and start codon (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP25 by PCR. SEQ ID NOs of the primers used can be found in Table III.

FIG. 28 depicts the predicted amino acid sequence of the Arabidopsis thaliana CCP25. The complete amino acid sequence corresponds to amino acids 1 to 724 of SEQ ID NO:120. Underlined is the predicted partial amino acid (SEQ ID NO:91) sequence.

FIG. 29 depicts the cDNA sequence of the Arabidopsis thaliana CCP26. The complete nucleotide sequence corresponds to nucleic acids 1 to 4002 of SEQ ID NO:55. Underlined is the partially characterized nucleotide (SEQ ID NO:26) sequence. Indicated are stop and start codon (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP26 by PCR. SEQ ID NOs of the primers used can be found in Table III. Nucleotide sequence differences between SEQ ID NOs:26 and SEQ ID NO:55 are depicted.

FIG. 30 depicts the predicted amino acid sequence of the Arabidopsis thaliana CCP26. The complete amino acid sequence corresponds to amino acids 1 to 1313 of SEQ ID NO:121. Underlined is the predicted partial amino acid (SEQ ID NO:92) sequence. Amino acid sequence differences between SEQ ID NOs:92 and SEQ ID NO:121 are depicted.

FIG. 31 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP27. The complete nucleotide sequence (FIG. 31A) corresponds to nucleic acids 1 to 1251 of SEQ ID NO:56. The complete amino acid sequence (FIG. 31B) corresponds to amino acids 1 to 310 of SEQ ID NO:122. Underlined in FIG. 31A and FIG. 31B are the partially characterized nucleotide (SEQ ID NO:27) and predicted partial amino acid (SEQ ID NO:93) sequence, respectively. Indicated in FIG. 31A are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP27 by PCR. SEQ ID NOs of the primers used can be found in Table III. Nucleotide sequence differences between SEQ ID NO:27 and SEQ ID NO:56 are depicted in FIG. 31A.

FIG. 32 depicts the cDNA sequence of the Arabidopsis thaliana CCP28. The complete nucleotide sequence corresponds to nucleic acids 1 to 2955 of SEQ ID NO:56. Underlined is the partially characterized nucleotide (SEQ ID NO:28) sequence. Indicated are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP28 by PCR. SEQ ID NOs of the primers used can be found in Table III. Nucleotide sequence differences between SEQ ID NO:28 and SEQ ID NO:57 are depicted.

FIG. 33 depicts the predicted amino acid sequence of the Arabidopsis thaliana CCP28. The complete amino acid sequence corresponds to amino acids 1 to 964 of SEQ ID NO:123. Underlined is the predicted partial amino acid (SEQ ID NO:94) sequence.

FIG. 34 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP29. The complete nucleotide sequence (FIG. 34A) corresponds to nucleic acids 1 to 546 of SEQ ID NO:29. The complete amino acid sequence (FIG. 34B) corresponds to amino acids 1 to 181 of SEQ ID NO:95. Indicated in FIG. 34A are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP29 by PCR. SEQ ID NOs of the primers used can be found in Table III.

FIG. 35 depicts the cDNA sequences and predicted amino acid sequences of the Arabidopsis thaliana CCP30. The complete nucleotide sequence (FIG. 35A) corresponds to nucleic acids 1 to 492 of SEQ ID NO:30. Indicated in FIG. 35A are the stop and start codons (both in black shaded boxes), the complete sense primer and part of the antisense primer (grey shaded boxes) used to amplify the coding region of CCP30 by PCR. SEQ ID NOs of the primers used can be found in Table III. However, after sequencing of the PCR product a sequence error in SEQ ID NO:30 was detected (boxed nucleotide ‘a’ in FIG. 35A not present) which caused a frame shift effectuating the CCP30 open reading frame. The putative correct cDNA sequence is given in FIG. 35B (nucleic acids 1 to 865 of SEQ ID NO:58) wherein the three putative start codons are marked by a black shaded box. The originally identified start codon is indicated in bold letters. The stop codon is unaltered. The amino acid sequence in FIG. 35C corresponds to amino acids 1 to 163 of SEQ ID NO:96, the protein encoded by the initially identified open reading frame of SEQ ID NO:30. The putative correct complete amino acid sequence in FIG. 35D corresponds to amino acids 1 to 222 of SEQ ID NO:124 which comprises the longest possible open reading frame. The Met residues corresponding to the three possible start codons in SEQ ID NO:58 (FIG. 35B) are bold faced.

FIG. 36 depicts the cDNA sequence of the Arabidopsis thaliana CCP31. The complete nucleotide sequence corresponds to nucleic acids 1 to 723 of SEQ ID NO:31. Indicated in FIG. 1A are the stop and start codons (both in black shaded boxes).

FIG. 37 depicts the predicted amino acid sequence of the Arabidopsis thaliana CCP31. The complete amino acid sequence corresponds to amino acids 1 to 148 of SEQ ID NO:125.

FIG. 38 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP32. The complete nucleotide sequence (FIG. 38A) corresponds to nucleic acids 1 to 426 of SEQ ID NO:60. The complete amino acid sequence (FIG. 38B) corresponds to amino acids 1 to 70 of SEQ ID NO:126. Underlined in FIG. 38A is the partially characterized nucleotide (SEQ ID NO:32) sequence. Indicated in FIG. 38A are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP32 by PCR. SEQ ID NOs of the primers used can be found in Table III. FIG. 38C gives the originally erroneously predicted amino acid sequence of CCP32 (amino acids 1 to 38 of SEQ ID NO:98).

FIG. 39 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP33. The complete nucleotide sequence (FIG. 39A) corresponds to nucleic acids 1 to 1442 of SEQ ID NO:61. The complete amino acid sequence (FIG. 39B) corresponds to amino acids 1 to 385 of SEQ ID NO:127. Indicated in FIG. 39A are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP33 by PCR. SEQ ID NOs of the primers used can be found in Table III. Indicated in FIG. 39B are the DNA binding domain (black shaded box), DEF domain (grey shaded box), DCB1 domain (single underlined) and DCB2 domain (double underlined), all domains characteristic for a DP protein.

FIG. 40 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP34. The complete nucleotide sequence (FIG. 40A) corresponds to nucleic acids 1 to 1506 of SEQ ID NO:62. The complete amino acid sequence (FIG. 40B) corresponds to amino acids 1 to 437 of SEQ ID NO:128. Underlined in FIG. 40A and FIG. 40B are the partially characterized nucleotide (SEQ ID NO:34) and predicted partial amino acid (SEQ ID NO:62) sequence, respectively. Indicated in FIG. 40A are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP34 by PCR. SEQ ID NOs of the primers used can be found in Table III.

FIG. 41 depicts the cDNA sequence of the Arabidopsis thaliana CCP35. The complete nucleotide sequence corresponds to nucleic acids 1 to 2631 of SEQ ID NO:63. Underlined is the partially characterized nucleotide (SEQ ID NO:35) sequence. Indicated are the stop and start codons (both in black shaded boxes) and of the primers (grey shaded boxes) used to amplify the coding region of CCP35 by PCR. SEQ ID NOs of the primers used can be found in Table III. Nucleotide sequence differences between SEQ ID NO:33 and SEQ ID NO:63 are depicted.

FIG. 42 depicts the predicted amino acid sequence of the Arabidopsis thaliana CCP35. The complete amino acid sequence corresponds to amino acids 1 to 749 of SEQ ID NO:129. Underlined is the predicted partial amino acid (SEQ ID NO:101) sequence.

FIG. 43 depicts the cDNA sequence of the Arabidopsis thaliana CCP36. The complete nucleotide sequence corresponds to nucleic acids 1 to 2743 of SEQ ID NO:64. Underlined is the partially characterized nucleotide (SEQ ID NO:36) sequence. Indicated are the stop and start codons (both in black shaded boxes). Nucleotide sequence differences between SEQ ID NO:36 and SEQ ID NO:64 are depicted.

FIG. 44 depicts the predicted amino acid sequence of the Arabidopsis thaliana CCP36. The complete amino acid sequence corresponds to amino acids 1 to 742 of SEQ ID NO:130. Underlined is the predicted partial amino acid (SEQ ID NO:102) sequence.

FIG. 45 depicts the cDNA sequence of the Arabidopsis thaliana CCP37. The complete nucleotide sequence corresponds to nucleic acids 1 to 2959 of SEQ ID NO:65. Underlined is the partially characterized nucleotide (SEQ ID NO:37) sequence. Indicated are the stop and start codons (both in black shaded boxes) and primers (grey shaded boxes) used to amplify the coding region of CCP45 by PCR. SEQ ID NOs of the primers used can be found in Table III.

FIG. 46 depicts the predicted amino acid sequence of the Arabidopsis thaliana CCP37. The complete amino acid sequence corresponds to amino acids 1 to 911 of SEQ ID NO:131. Underlined is the predicted partial amino acid (SEQ ID NO:103) sequence. Indicated in a black shaded box is a SAP-like domain.

FIG. 47 depicts the cDNA sequence and predicted amino acid sequence of the Arabidopsis thaliana CCP38. The complete nucleotide sequence (FIG. 47A) corresponds to nucleic acids 1 to 1295 of SEQ ID NO:66. The complete amino acid sequence (FIG. 47B) corresponds to amino acids 1 to 357 of SEQ ID NO:132. Underlined in FIG. 47A and FIG. 47B arc the partially characterized nucleotide (SEQ ID NO:38) and predicted partial amino acid (SEQ ID NO:104) sequence, respectively. Indicated in FIG. 47A are the stop and start codons (both in black shaded boxes) which are part of the primers (grey shaded boxes) used to amplify the coding region of CCP38 by PCR. SEQ ID NOs of the primers used can be found in Table III.

FIG. 48 depicts phosphorylation of the Arabidopsis thaliana CCP4 by CDKs. The protein CDC2bDN-IC26M (SEQ ID NO:70) contains a consensus CDK phosphorylation site (TPWK, residues 54-57 of SEQ ID NO:263). The corresponding gene (SEQ ID NO:4) was expressed in E. coli and the protein was purified from the crude extracts. The purified protein was subsequently shown to be phosphorylated by CDKs in an in vitro CDK phosphorylation assay. −: no IC₂₆M added; +: IC26M added.

FIG. 49 schematically represents the domain organization of AtE2Fa and AtE2Fb. The DNA-binding domain (DB), the dimerization domain (DIM), the marked box (MB), and the Rb-binding domain (RB) are indicated by marked boxes, the N-terminal domains are indicated by open boxes. Numbering on the right refers to the amino acid sequence contained in the different AtE2F constructs, which were used in the in vitro binding assays.

FIG. 50 depicts AtDPa in vitro interactions with AtE2Fa and AtE2Fb. The c-myc-tagged AtDPa (c-myc-AtDPa) was in vitro translated and used as control. The lower migrating proteins observed in the case of c-myc-AtDPa are most probably due to initiation of translation at internal methionine codons (panel A, unnumbered left lane). The c-myc-AtDPa was in vitro co-translated with HA-AtE2Fb (panels A and B, lane 1), HA-AtE2Fa (panels B, lane 2), the C-terminal deleted form of HA-AtE2Fb (panels A and B, lane 3), HA-AtE2Fa 1-420 (panels A and B, lane 4) and the N-terminal truncated form of HA-AtE2Fa 162-485 (panels A and B, lane 5) as indicated. Numbers in the case of the mutant AtE2Fs refer to the amino acid sequence contained in these constructs (see FIG. 49). An aliquot of each sample was analyzed directly by SDS-PAGE and autoradiographed (panel A; total IVT, total in vitro translation). Another aliquot of the same samples was subjected to immunoprecipitation with anti-c-myc monoclonal antibodies (panel B), lanes are indicated by numbering. The position of c-myc-AtDPa proteins are marked by arrows in both panels. Molecular mass markers are indicated at the left.

FIG. 51 shows AtDPb in vitro interactions with AtE2Fa and AtE2Fb. The c-myc-tagged AtDPb (c-myc-AtDPb, panels A and B, lane 2) and the HA-tagged AtE2Fb (HA-AtE2Fb, panels A and B, lane 1) were in vitro translated and used as controls. The lower migrating proteins observed in the case of c-myc-AtDPb are most probably due to initiation of translation at internal methionine codons (panel A, lane 2). The c-myc-AtDPb was in vitro co-translated with HA-AtE2Fb (panels A and B, lane 3), HA-AtE2Fa (panels A and B lane 4), HA-AtE2Fa 1-420 (panels A and B, lane 5) and the N-terminal truncated form of HA-AtE2Fa 162-485 (panels A and B, lane 6) as indicated. Numbers in the case of the mutant AtE2Fs refer to the amino acid sequence contained in these constructs (see FIG. 49). An aliquot of each sample was analyzed directly by SDS-PAGE and autoradiographed (panel A; total IVT, total in vitro translation). Another aliquot of the same samples was subjected to immunoprecipitation with anti-c-myc monoclonal antibodies (panel B), lanes are indicated by numbering. The c-myc-AtDPb (panels A and B, lanes 2-6; indicated with ‘y’) co-migrated almost exactly with the mutant HA-AtE2Fa 1-420 (panels A and B, lane 5; indicated with ‘x’) and HA-AtE2Fa 162-485 (panels A and B, lane 6; indicated with ‘z’) in the gel system. These polypeptides as well as the position of c-myc-AtDPa and c-myc-AtDPb proteins are marked by arrows marked with ‘y’, ‘x’ and ‘z’, respectively (cfr. supra). Molecular mass markers are indicated at the left.

FIG. 52 schematically represents AtDPa and mutants. The DNA-binding domain (DB) and the dimerization domain (DIM) are indicated by marked boxes, N- and C-terminal regions are indicated by open boxes. Numbering on the right side refers to the amino acid sequence contained in the different AtDP constructs, which were used in the in vitro binding assays.

FIG. 53 schematically represents AtDPb and mutants. The DNA-binding domain (DB) and the dimerization domain (DIM) are indicated by marked boxes, N- and C-terminal regions are indicated by open boxes. Numbering on the right side refers to the amino acid sequence contained in the different AtDP constructs, which were used in the in vitro binding assays.

FIG. 54 shows the mapping of regions in AtDPa required for in vitro binding to AtE2Fb. HA-AtE2Fb was co-translated with series of c-myc-AtDPa mutants. An aliquot of each sample was analyzed directly by SDS-PAGE and autoradiographed (panel A). Another aliquot of the same samples was subjected to immunoprecipitation with anti-HA (panel B) or anti-c-myc (panel C) monoclonal antibodies. The c-myc-AtDPa mutants are marked by dots. Positions of the HA-AtE2Fb proteins are indicated by arrows. Molecular mass markers are indicated at the left.

FIG. 55 shows the mapping of regions in AtDPb required for in vitro binding to AtE2Fb. HA-AtE2Fb was co-translated with series c-myc-AtDPb mutants. An aliquot of each sample was analyzed directly by SDS-PAGE and autoradiographed (panel A). Another aliquot of the same samples was subjected to immunoprecipitation with anti-HA (panel B) or anti-c-myc (panel C) monoclonal antibodies. The c-myc-AtDPb mutants are marked by dots. Positions of the HA-AtE2Fb proteins are indicated by arrows. Molecular mass markers are indicated at the left.

FIG. 56 shows the mapping of regions in AtDPb required for in vitro binding to AtE2Fb. HA-AtE2Fb was co-translated with c-myc-AtDPb 182-263. Because of the small size of this protein, it was hardly detectable when it was directly analyzed by SDS-PAGE (data not shown). An aliquot of this sample was subjected to immunoprecipitation with anti-c-myc monoclonal antibodies. The c-myc-AtDP mutant is marked by dots. Position of the HA-AtE2Fb protein is indicated by an arrow. Molecular mass markers are indicated at the left.

FIG. 57 shows organ- and cell cycle-specific expression of AtE2Fa and AtDPa. Tissue-specific expression of AtDPa and AtE2Fa genes. cDNA prepared from the indicated tissues was subjected to semi-quantitative RT-PCR analysis. The Arath; CDKB1; 1 gene was used as a marker for highly proliferating tissues. The actin 2 gene (ACT2) was used as loading control.

FIG. 58 shows organ- and cell cycle-specific expression of AtE2Fa and AtDPa. Co-regulated cell cycle phase-dependent transcription of AtE2Fa and AtDPa. The cDNA was prepared from partially synchronized Arabidopsis cells harvested at the indicated time point after removal of the cell cycle blocker was subjected to semi-quantitative RT-PCR analysis. Histone H4 and Arath;CDKB1;1 were used as markers for S and G2/M phase, respectively, and ROCS and Arath;CDKA;1 as loading controls.

FIG. 59 is a photographic representation of Northern blotting analysis of DPa expression in independent Arabidopsis thaliana DPa overexpressing lines (lines 16-27 as indicated) and one untransformed control line (indicated by C).

FIG. 60 describes the molecules defined in SEQ ID NOs:199-204 and 240-290.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is based, at least in part, on the discovery of novel molecules, referred to herein as “cell cycle proteins” or “CCP” nucleic acid and polypeptide molecules. The CCP molecules of the present invention were identified based on their ability, as determined using yeast two-hybrid assays (described in detail in Example 1), to interact with proteins involved in the cell cycle, such as plant cyclin dependent kinases (e.g., a dominant negative form of CDC2b, CDC2bAt.N161), cyclin dependent kinase subunits referred herein as “CKS” (such as CKS1At), cyclin dependent kinase inhibitors referred to herein as “CKI” (such as CKI4), PHO80-like proteins referred to herein as “PLP”, E2F, and different domains of kinesin-like proteins referred to herein as “KLPNT.

Because of their ability to interact with (e.g., bind to) the cyclin dependent kinases, the CCP molecules of the present invention may modulate, e.g., upregulate or downregulate, the activity of plant CDKs, such as CDC2a or CDC2b; CKSs, CKIs, PLPs and KLPNTs. Furthermore, because of their ability to interact with (e.g., bind to) the aforementioned proteins which are proteins involved in cell cycle regulation, the CCP molecules of the present invention may also play a role in or function in cell cycle regulation, e.g., plant or animal cell cycle regulation.

As used herein, the term “cell cycle protein” includes a polypeptide which is involved in controlling or regulating the cell cycle, or part thereof, in a cell, tissue, organ or whole organism. Cell cycle proteins may also be capable of binding to, regulating, or being regulated by cyclin dependent kinases, such as plant cyclin dependent kinases, e.g., CDC2a or CDC2b, or their subunits. The term cell cycle protein also includes peptides, polypeptides, fragments, variant, homologs, alleles or precursors (e.g., pre-proteins or pro-proteins) thereof.

As used herein, the term “cell cycle” includes the cyclic biochemical and structural events associated with growth, division and proliferation of cells, and in particular with the regulation of the replication of DNA and mitosis. The cell cycle is divided into periods called: G₀, Gap₁ (G₁), DNA synthesis (S), Gap₂ (G₂), and mitosis (M). Normally these four phases occur sequentially, however, the cell cycle also includes modified cycles wherein one or more phases are absent resulting in modified cell cycle such as endomitosis, acytokinesis, polyploidy, polyteny, and endoreduplication.

As used herein, the term “plant” includes reference to whole plants, plant organ (e.g., leaves, stems, roots), plant tissue, seeds, and plant cells and progeny thereof. Plant cell, as used herein includes, without limitation, seeds, e.g., seed suspension cultures, embryos, meristematic regions, callus tissue, leaves, roots, shoots, gametophytes, sporophytes, pollen, and microspores. The class of plants which can be used in the methods of the invention is generally as broad as the class of higher plants amenable of transformation techniques, including both monocotyledonous and dicotyledonous plants. Particularly preferred plants are Arabidopsis thaliana, rice, wheat, maize, tomato, alfalfa, oilseed rape, soybean, cotton, sunflower or canola. The term plant also includes monocotyledonous (monocot) plants and dicotyledonous (dicot) plants including a fodder or forage legume, ornamental plant, food crop, tree, or shrub selected from the list comprising Acacia spp., Acer spp., Actinidia spp., Aesculus spp., Agathis australis, Albizia amara, Alsophila tricolor, Andropogon spp., Arachis spp, Areca catechu, Astelia fragrans, Astragalus cicer, Baikiaea plurijuga, Betula spp., Brassica spp., Bruguiera gymnorrhiza, Burkea africana, Buteafrondosa, Cadaba farinosa, Calliandra spp, Camellia sinensis, Canna indica, Capsicum spp., Cassia spp., Centroema pubescens, Chaenomeles spp., Cinnamomum cassia, Coffea arabica, Colophospermum mopane, Coronillia varia, Cotoneaster serotina, Crataegus spp., Cucumis spp., Cupressus spp., Cyathea dealbata, Cydonia oblonga, Cryptomeria japonica, Cymbopogon spp., Cynthea dealbata, Cydonia oblonga, Dalbergia monetaria, Davallia divaricata, Desmodium spp., Dicksonia squarosa, Diheteropogon amplectens, Dioclea spp, Dolichos spp., Dorycnium rectum, Echinochloa pyramidalis, Ehrartia spp., Eleusine coracana, Eragrestis spp., Erythrina spp., Eucalyptus spp., Euclea schimperi, Eulalia villosa, Fagopyrum spp., Feijoa sellowiana, Fragaria spp., Flemingia spp, Freycinetia banksii, Geranium thunbergii, Ginkgo biloba, Glycine javanica, Gliricidia spp, Gossypium hirsutum, Grevillea spp., Guibourtia coleosperma, Hedysarum spp., Hemarthia altissima, Heteropogon contortus, Hordeum vulgare, Hyparrhenia rufa, Hypericum erectum, Hyperthelia dissoluta, Indigo incarnata, Iris spp., Leptarrhena pyrolifolia, Lespediza spp., Lettuca spp., Leucaena leucocephala, Loudetia simplex, Lotonus bainesii, Lotus spp., Macrotyloma axillare, Malus spp., Manihot esculenta, Medicago sativa, Metasequoia glyptostroboides, Musa sapientum, Nicotianum spp., Onobrychis spp., Ornithopus spp., Oryza spp., Peltophorum africanum, Pennisetum spp., Persea gratissima, Petunia spp., Phaseolus spp., Phoenix canariensis, Phormium cookianum, Photinia spp., Picea glauca, Pinus spp., Pisum sativum, Podocarpus totara, Pogonarthria fleckii, Pogonarthria squarrosa, Populus spp., Prosopis cineraria, Pseudotsuga menziesii, Pterolobium stellatum, Pyrus communis, Quercus spp., Rhaphiolepsis untbellata, Rhopalostylis sapida, Rhus natatlensis, Ribes grossularia, Ribes spp., Robinia pseudoacacia, Rosa spp., Rubus spp., Salix spp., Schyzachyrium sanguineum, Sciadopitys verticillata, Sequoia sempervirens, Sequoiadendron giganteum, Sorghum bicolor, Spinacia spp., Sporobolus fimbriatus, Stiburus alopecuroides, Stylosanthos humilis, Tadehagi spp, Taxodium distichum, Themeda triandra, Trifolium spp., Triticum spp., Tsuga heterophylla, Vaccinium spp., Vicia spp. Vitis vinifera, Watsonia pyramidata, Zantedeschia aethiopica, Zea mays, amaranth, artichoke, asparagus, broccoli, brussel sprout, cabbage, canola, carrot, cauliflower, celery, collard greens, flax, kale, lentil, oilseed rape, okra, onion, potato, rice, soybean, straw, sugarbeet, sugar cane, sunflower, tomato, squash, and tea, amongst others, or the seeds of any plant specifically named above or a tissue, cell or organ culture of any of the above species.

The cell cycle proteins of the present invention are involved in cell cycle regulation which is largely, but not completely, similar in plants and animals Accordingly, the nucleic acid molecules and polypeptide of the invention, or derivatives thereof, may be used to modulate the cell cycle in a plant or an animal such as by modulating the activity or level or expression of CCP, altering the rate of the cell cycle or phases of the cell cycle, and entry into and out of the various cell cycle phases. In plants, the molecules of the present invention may be used in agriculture to, for example, improve the growth characteristics of plant such as growth rate or size of specific tissues or organs, the architecture or morphology of the plant, increase crop yield, improve tolerance to environmental stress conditions (such as drought, salt, temperature, or nutrient deprivation), improve tolerance to plant pathogens that abuse the cell cycle or as targets to facilitate the identification of inhibitors or activators of CCPs that may be useful as phytopharmaceuticals such as herbicides or plant growth regulators.

As used herein, the term “cell cycle associated disorders” includes a disorder, disease or condition which is caused or characterized by a misregulation (e.g., downregulation or upregulation), abuse, arrest, or modification of the cell cycle. In plants cell cycle associated disorders include endomitosis, acytokinesis, polyploidy, polyteny, and endoreduplication which may be caused by external factors such as pathogens (nematodes, viruses, fungi, or insects), chemicals, environmental stress (e.g., drought, temperature, nutrients, or UV) resulting in for instance neoplastic tissue (e.g., galls, root knots) or inhibition of cell division/proliferation (e.g., stunted growth). Cell cycle associated disorders in animals include proliferative disorders or differentiative disorders, such as cancer, e.g., melanoma, prostate cancer, cervical cancer, breast cancer, colon cancer, or sarcoma.

The present invention is based, at least in part, on the discovery of novel molecules, referred to herein as CCP protein and nucleic acid molecules, which comprise a family of molecules having certain conserved structural and functional features. The term “family” when referring to the protein and nucleic acid molecules of the invention is intended to mean two or more proteins or nucleic acid molecules having a common structural domain or motif and having sufficient amino acid or nucleotide sequence homology as defined herein. Such family members can be naturally or non-naturally occurring and can be from either the same or different species. For example, a family can contain a first protein of plant, e.g. Arabidopsis, origin, as well as other, distinct proteins of plant, e.g., Arabidopsis, origin or alternatively, can contain homologues of other plants, e.g., rice, or of non-plant origin. Members of a family may also have common functional characteristics.

In one embodiment of the invention, a CCP protein of the present invention is identified based on the presence of at least one or more of the following domains:

A. Cyclin Destruction Box

As used herein, the term “Cyclin destruction box” includes a domain of 9-10 amino acid residues in length which typically contains the following consensus pattern:

(SEQ ID NO: 267) R-X₂-L-X₂-[I/V]-X₁₋₂-N, wherein X can be any amino acid, X_(n) is a stretch of n Xs, X_(n-m) is a stretch of n to m Xs, and wherein [I/V] means that an Ile or Val residue can occur at that position. SEQ ID NO:267 depicts the minimal consensus sequence of the cyclin destruction box and underlies the ubiquitin-mediated proteolytic destruction of the cyclins bearing this motif (Yarnano et al. (1998), EMBO J. 17: 5670-5678; Renaudin et al. (1998) in Plant Cell Division (Francis, Dudits and Inze, eds.), Portland Press Research Monograph, Portland Press Ltd. London (1998), pp 67-98).

B. Cyclin Box Motif 1

As used herein, the term “Cyclin box motif 1” includes a domain of 8 amino acid residues in length and which typically contains the following consensus pattern:

(SEQ ID NO: 268) MRXIL[I/V]DW, wherein X can be any amino acid and wherein [I/V] means that an Ile or Val residue can occur at that position. This motif forms part of the helix H1 of the first cyclin fold and is the best conserved motif in the cyclinA/B family (Renaudin et al. (1998) in Plant Cell Division (Francis, Dudits and Inzé, eds.), Portland Press Research Monograph, Portland Press Ltd. London (1998), pp 67-98).

C. Cyclin Box Motif 2

As used herein, the term “Cyclin box motif 2” includes a domain of 8 amino acid residues in length and which typically contains the following consensus pattern:

(SEQ ID NO: 269) KYEE-X₃-P, wherein X can be any amino acid and wherein X_(n) is a stretch of n Xs. This motif forms part of the helix H3 of the first cyclin fold wherein the 2 acidic residues are part of the CDK binding site (Renaudin et al. (1998) in Plant Cell Division (Francis, Dudits and Inzé, eds.), Portland Press Research Monograph, Portland Press Ltd. London (1998), pp 67-98).

D. CDC2 Motifs

As used herein, the term “CDC2 motifs” includes domains of about 9-12 amino acid residues in length and which typically contain one of the following consensus patterns:

(SEQ ID NO: 270) GXG-X₂₋GXVY (SEQ ID NO: 271) HRDXK-X₂-NXL (SEQ ID NO: 272) D-X₁₋₂-[W/Y]SXG-X₄-E wherein X can be any amino acid, X_(n) is a stretch of n Xs, X_(n-m) is a stretch of n to m Xs, and wherein [W/Y] means that an Trp or Tyr residue can occur at that position.

E. CDK Phosphorylation Site

As used herein the term “CDK phosphorylation site” includes a domain of about 5-7 amino acids in length and which contains one or more of the following consensus

(SEQ ID NO: 273) TPX₁₋₂[R/K] (SEQ ID NO: 274) SPX[R/K] (SEQ ID NO: 275) SPX(Hu) (SEQ ID NO: 276) SP(Hu)X with Hu being a hydrophobic uncharged amino acid (M, I, L, V) and X any amino acid. The foregoing are typically found in cyclin-dependent kinase substrates such as histone kinase, transcription factors such as E2F or transcription regulators like Rb. CDK phosphorylation sites are described in, for example, Tamrakar et al. 2000, Frontiers Biosci 5, d121-137.

CCP proteins of the present invention comprising a CDK phosphorylation site can be mutated in said CDK phosphorylation site such that said CCP proteins are no longer able to be phosphorylated on the CDK phosphorylation site. Mutations of a CDK phosphorylation site include all mutations of the ser or thr residue in any of SEQ ID NOs:273-276 into a non-phosphorylatable amino acid residue, e.g., an ala or glu residue. Mutation of one or more CDK phosphorylation site(s) in a CCP protein of the invention is expected to modulate modifications of the CCP protein by CDKs and, thus, to modulate the biological or biochemical function of the CCP protein.

F. E Nuclear Localisation Signal (NLS)

As used herein the term “nuclear localization signal” or “NLS” includes a domain conferring to a protein comprising the NLS domain the ability to be imported into the nucleus and to, for example, accumulate within the nucleus. NLS domains include one or more of the following concensus patterns:

(SEQ ID NO: 277) PKKKRKV (SEQ ID NO: 278) KRX₁₀KKKK (SEQ ID NO: 279) KRPRP (SEQ ID NO: 280) PAAKRVKLD

NLS domains have been found in the SV40 T antigen, in nucleoplasmin (bipartite NLS), in a Adeno EIA, and in c-Myc. NLS domains are described in, for example, Laskey et al. (1998) Biochem. Soc. Trans. 26, 561-567.

G. Cy-Like Boxes

As used herein, the term “Cy-like box” includes a domain of 3-6 amino acid residues in length with has the consensus motif R-X-X-F (SEQ ID NO:281) with X being any amino acid and one of two Xs preferably being a hydrophobic residue.

H. Rb Binding Domain

As used herein, the term “Rb binding domain” includes a domain which when present in a protein confers to the protein the ability to bind the Rb protein. Rb binding domains include one or more of the following concensus patterns:

(SEQ ID NO: 282) LXCXE (SEQ ID NO: 283) LXSXE (SEQ ID NO: 284) DYX₇EX₃DLFD (SEQ ID NO: 285) DYX₆DX₄DMWE Rb binding domains have been found in D-cyclins, in protein phosphatase 1, in human E2F-1, and in plant E2F. Rb binding domains are described in, for example, Rubin et al. (1998) Frontiers Eiosci 3, d1209-1219; Phelps et al. (1992) J. Virol. 66, 2418-2427, and Cress et al. (1993) Mol. Cell. Biol. 13, 6314-6325.

I. DEF Domain

As used herein the term “DEF domain” includes a protein domain which is required for the formation of heterodimers between DP proteins and E2F proteins. DEF domains comprise the following concensus pattern:

(SEQ ID NO: 286) [D/N/-][Q/E]KNIR[R/G]RV[Y/D]DALNV[L/F]MA[M/I/L/-] [N/D][V/I]I[S/A][K/R][D/E]KKEI[K/Q/R/-]W[R/K/I]GLP

J. DNA Binding Domain

As used herein the term “DNA binding domain” includes a domain which is involved in the binding of DP proteins and/or DP-E2F heterodimers to DNA. DNA binding domains include the following concensus pattern:

(SEQ ID NO: 287) [G/N][K/R]GLR[H/Q]FS[M/V][K/M][I/V]X₍₀₋₁₇₎C[E/Q]K[V/L][Q/E/-][S/-]XK[G/K]- [R/I/-]TT[S/-]Y[N/K]EVADE[L/I][V/I][A/S][E/D]F DNA binding domains are described in, for example, Hao et al. (1995) J. Cell Sci. 108, 2945-2954; Bandara et al. (1993) EMBO J. 12, 4317-4324; and Girling et al. (1994) Mol. Biol. Cell 5, 1081-4092.

K. DCB1 Domain:

As used herein the term “DCB1 domain” includes a protein domain which is conserved among DP proteins and has the following consensus patterns:

(SEQ ID NO: 288) [R/S][I/V]X[Q/K]KX₃[L/S]XE (SEQ ID NO: 289) [R/S][I/V]X[Q/K]KX₃[L/S]XE[L/M]X₂₋₃[Q/H]X₄₋₅NL[V/I/M][Q/E]RN DCB1 domains are described in, for example, Hao et al. (1995) J. Cell Sci. 108, 2945-2954; Bandara et al. (1993) EMBO J. 12, 4317-4324; and Girling et al. (1994) Mol. Biol. Cell 5, 1081-1092.

L. DCB2 Domain:

As used herein the term “DCB2 domain” includes a protein domain which is conserved among DP proteins and has the following consensus patern:

(SEQ ID NO: 290) [L/I]PFI[L/I][V/L]XTX₃₋₄[T/V]VX₁₂₋₁₄FX₃₋₄F[E/S][Hu]HDDX₂[V/I]L[R/K]XM DCB2 domains are described in, for example, Hao et al. (1995) J. Cell Sci. 108, 2945-2954; Bandara et al. (1993) EMBO J. 12, 4317-4324; and Girling et al. (1994) Mol. Biol. Cell 5, 1081-1092.

M. SAP Domain:

As used herein the term SAP motif includes a protein domain of about 35 amino acid residues which is found in a variety of nuclear proteins involved in transcription, DNA repair, DNA processing or apoptotic chromatin degradation. It was named after SAF-A/B, Acinus and PIAS, three proteins known to contain it. The SAP motif reveals a bipartite distribution of strongly conserved hydrophobic, polar and bulky amino acids separated by a region that contains a glycine. The SAP domain has been proposed to be a DNA-binding motif (Aravind and Koonin (2000) Trends Biochem. Sci. 25:112-114).

Isolated CCP proteins of the present invention have an amino acid sequence sufficiently identical to the amino acid sequence of SEQ ID NO:67-132, 205, 211, 215-216, or 220-227 or are encoded by a nucleotide sequence sufficiently identical to SEQ ID NO:1-66 or 228-239. As used herein, the term “sufficiently identical” refers to a first amino acid or nucleotide sequence which contains a sufficient or minimum number of identical or equivalent (e.g., an amino acid residue which has a similar side chain) amino acid residues or nucleotides to a second amino acid or nucleotide sequence such that the first and second amino acid or nucleotide sequences share common structural domains or motifs and/or a common functional activity. For example, amino acid or nucleotide sequences which share common structural domains have at least 30%, 40%, or 50% homology, preferably 60% homology, more preferably 70%-80%, and even more preferably 90-95% homology across the amino acid sequences of the domains and contain at least one and preferably two structural domains or motifs, are defined herein as sufficiently identical. Furthermore, amino acid or nucleotide sequences which share at least 30%, 40%, or 50%, preferably 60%, more preferably 70-80%, or 90-95% homology and share a common functional activity are defined herein as sufficiently identical.

As used interchangeably herein, an “CCP activity”, “biological activity of CCP” or “functional activity of CCP”, refers to an activity exerted by a CCP protein, polypeptide or nucleic acid molecule on a CCP responsive cell or tissue, or on a CCP protein substrate, as determined in vivo, or in vitro, according to standard techniques. In one embodiment, a CCP activity is a direct activity, such as an association with a CCP-target molecule. As used herein, a “target molecule” or “binding partner” is a molecule with which a CCP protein binds or interacts in nature, such that CCP-mediated function is achieved. A CCP target molecule can be a non-CCP molecule or a CCP protein or polypeptide of the present invention, e.g., a plant cyclin dependent kinase, such as CDC2b. In an exemplary embodiment, a CCP target molecule is a CCP ligand. Alternatively, a CCP activity is an indirect activity, such as a cellular signaling activity mediated by interaction of the CCP protein with a CCP ligand. The biological activities of CCP are described herein. For example, the CCP proteins of the present invention can have one or more of the following activities: (1) they may interact with a non-CCP protein molecule, e.g., a CCP ligand; (2) they may modulate a CCP-dependent signal transduction pathway; (3) they may modulate the activity of a plant cyclin dependent kinase, such as CDC2a, CDC2b, or CDC2c, and (4) they may modulate the cell cycle.

Accordingly, another embodiment of the invention features isolated CCP proteins and polypeptides having a CCP activity. Preferred proteins are CCP proteins having at least one or more of the following domains: a “cyclin destruction box”, a “cyclin box motif 1”, a “cyclin box motif 2”, a “CDC2 motif”, a “CDK phosphorylation site”, a “nuclear localization signal”, a “Cy-like box”, an “Rb binding domain”, a “DEF domain”, a “DNA binding domain”, a “DCB1 domain”, a “DCB2 domain” and/or a SAP domain, and, preferably, a CCP activity.

Additional preferred proteins have at least one or more of the following domains: a “cyclin destruction box”, a “cyclin box motif 1”, a “cyclin box motif 2”, a “CDC2 motif”, a “CDK phosphorylation site”, a “nuclear localization signal”, a “Cy-like box”, an “Rb binding domain”, a “DEF domain”, a “DNA binding domain”, a “DCB1 domain”, a “DCB2 domain” and/or a SAP domain and are, preferably, encoded by a nucleic acid molecule having a nucleotide sequence which hybridizes under stringent hybridization conditions to a nucleic acid molecule comprising the nucleotide sequence of SEQ ID NO:1-66 or 228-239.

The sequences of the present invention are summarized below, in Table I.

TABLE I SEQ ID NO: SEQ ID NO: SEQ ID NO: SEQ ID NO: CCP Clone Homolog/ partial full-length partial full-length Molecule Name Bait function motif DNA DNA Protein Protein CCP1 CDC2bD CDC2bAt. Novel CYCB2; 3 cyclin box 1 39 67 105 N-IC19 N161 motifs 1 and 2; cyclin destruction box CCP2 CDC2bD CDC2bAt. ARR2 2 40 68 106 N-IC20 N161 CCP3 CDC2bD CDC2bAt. novel A-type cyclin box 3 41 69 107 N-IC21 N161 cyclin motifs 1 and 2; cyclin destruction box CCP4 CDC2bD CDC2bAt. CDK 4 4 70 70 N-IC26M N161 phosphorylation site CCP5 CDC2bD CDC2bAt. Arath cyclin box 5 5 71 71 N-IC39 N161 CYCB2; 1 motifs 1 and 2; cyclin destruction box CCP6 CDC2bD CDC2bAt. 6 42 72 108 N-IC57 N161 CCP7 CDC2bD CDC2bAt. AJH2-COP9 7 43 73 109 N-IC62 N161 CCP8 E2F3ca55 E2F3 N- 8 43 74 109 terminal CCP9 CDC2bD CDC2bAt. Arath cyclin box 9 9 75 75 N-IC9 N161 CYCA2; 2 motifs 1 and 2; cyclin destruction box CCP10 CKSBC001 CKS1At 10 10 76 76 CCP11 CKSBC011 CKS1At gibberellin- 11 44 77 110 regulated protein GASA1 precursor CCP12 CKSBC9 CKS1At 12 45 78 111 8-7 (Cterm) CCP13 CKSBC9 CKS1At 13 45 79 111 8-7 (Nterm) CCP14 CKSBC1 CKS1At 14 46 80 112 03-19 (Cterm) CCP15 CKSBC1 CKS1At PSTTLRE-type CDC2 15 47 81 113 99-20 CDK motifs CCP16 E2F5BB E2F5 DPa DNA-binding 16 48 82 114 C1 dimerisation domain; DEF domain domain; DCB1 and DCB2 domain CCP17 FL67BC4- CKI4 17 17 83 83 2 CCP18 FL67BC12- CKI4 RNA 18 49 84 115 17 polymerase B transcription factor 3 CCP19 JUT1 PLP1 19 19 85 85 CCP20 JUT2 PLP1 20 50 86 116 CCP21 JUT3 PLP1 21 50 87 116 CCP22 JUT6 PLP1 Submergence 22 51 88 117 induced protein2 or Oryza sativa CCP23 kbp1 KLPNT1 HSF1 23 52 89 118 36-508aa (motor domain) KLPNT2 (TH65) 73-186 aa (neck domain) CCP24 kbp3 KLPNT1 24 53 90 119 (427- 867aa) stalk domain CCP25 kbp6 KLPNT2 25 54 91 120 (TH65) 73-186 aa neck domain CCP26 kbp9 KLPNT2 AtKLPNT1 26 55 92 121 (TH65) 73-186 aa neck domain CCP27 kbp11 KLPNT2 27 56 93 122 (TH65) 73-186 aa neck domain CCP28 kbp12 KLPNT2 28 57 94 123 (TH65) 73-186 aa neck domain CCP29 kbp13 KLPNT2 29 29 95 95 (TH65) 73-186 aa neck domain CCP30 kbp15 KLPNT2 Centromere/ 30 58 96 124 (TH65) microtubule 73-186 aa binding neck protein CBF5 domain from yeast CCP31 kbp20 KLPNT2 VU91C 31 59 97 125 (TH65) calmodulin 73-608 aa from yeast stalk domain CCP32 E2F5BB E2F5 32 60 98 126 C16 dimerization CCP33 DPb / DNA-binding 33 61 99 127 domain; DEF domain; DCB1 and DCB2 domain CCP34 E2F3ca1 E2F3 N- 34 62 100 128 terminal CCP35 E2F3ca2 E2F3 N- 35 63 101 129 terminal CCP36 E2F3ca9 E2F3 N- 36 64 102 130 terminal CCP37 E2F3ca12 E2F3 N- SAP 37 65 103 131 terminal domain CCP38 E2F3ca50 E2F3 N- 38 66 104 132 terminal

Detailed studies of interactions between AtDPs (a and b forms, SEQ ID NO:114 and SEQ ID NO:127, respectively) and AtE2Fs (a and b forms; GenBank accession numbers AJ294534 and AJ294533, respectively) revealed that the regions of AtDPa and AtDPb involved in the binding of AtE2Fb are different.

Binding of AtDPa to AtE2Fb requires at least the AtDPa dimerization domain and the whole (or possibly part of) the C-terminal domain of AtDPa. The N-terminal domain and the DNA-binding domain of AtDPa do not seem to contribute to the interaction of AtDPa with AtE2Fb (Examples 11, 12, Table 5, FIG. 54).

Binding of AtDPb to AtE2Fb, however, only requires an intact AtDPb dimerization domain. Neither the region including the N-terminal and DNA-binding domains of AtDPb, nor the C-terminal region of AtDPb seem to contribute to the interaction of AtDPb with AtE2Fb (Examples 11, 12, Table 5, FIG. 55). These observations indicate that modulating the formation of specific E2F/DP-complexes may be useful in modulating cell cycle traversal and the regulation thereof.

AtDPa and AtDPb, respectively, do not form homodimers but both interact with either AtE2Fa or AtE2Fb (Example 12, Table 5). In reciprocal experiments it was shown that the N-terminal domain of AtE2Fa is not required for binding AtDPa or AtDPb. Likewise, the Rb-binding domains of AtE2Fa and AtE2Fb, respectively, do not seem to contribute to the binding to either AtDPa or AtDPb. The region of AtE2Fa encompassing the dimerization domain and the marked box is sufficient for binding to AtDPa and AtDPb (Examples 11, 12, FIG. 50, FIG. 51, Table 5). The dimerization domain of AtE2Fs appears to be sufficient for binding to AtDPs.

Accordingly, it is shown herein for the first time (for plant DPs and plant E2Fs) that the minimal DP and E2F proteins or corresponding coding DNA Sequences that can be used in modifying E2F/DP-related processes, e.g., regulation of gene expression by E2F/DP, include:

(A) Plant DP dimerization domain with or without (part of) the C-terminal DP domain. These domains include the proteins AtDPa143-292 and AtDPa143-213 (numbering indicates the amino acids included in said fragment relative to the full-length AtDPa protein) set forth in SEQ ID NO:221 and SEQ ID NO:222, respectively. The coding sequences corresponding to the foregoing amino acid sequences are set forth in SEQ ID NO:232 and SEQ ID NO:233, respectively. Also included are the corresponding regions of the AtDPb protein characterized by AtDPb182-385 and AtDPb 182-263 (parts of the full-length AtDPb protein). The foregoing regions of AtDPb are set forth in SEQ ID NO:216 and SEQ ID NO:215, respectively, and the coding sequences corresponding thereto are set forth in SEQ ID NO:231 and SEQ ID NO:230, respectively. The AtDPb1-263 domain (SEQ ID NO:223) and the corresponding AtDPa1-214 domain (SEQ ID NO:220) encoded by the nucleic acid sequences SEQ ID NO:234 and SEQ ID NO:239, respectively, can also be used. Further included are nucleic acid sequences hybridizing to SEQ ID NOs:229-234 or SEQ ID NO:239 or encoding a protein at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98% or more identical to SEQ ID NOs:211, 215-216 and 220-223.

(B) Plant E2F dimerization domain with or without (part of) the marked box. These domains include the proteins AtE2Fa232-282, AtE2Fa232-352 and AtE2Fa226-356 set forth in SEQ ID NO:224, SEQ ID NO:225 and SEQ ID NO:205, respectively. The corresponding coding DNA sequences are set forth in SEQ ID NO:235, SEQ ID NO:236 and SEQ ID NO:228, respectively. Also included are the corresponding regions of the AtE2Fb protein characterized by AtE2Fb194-243 and AtE2Fb194-311 set forth in SEQ ID NO:226 and SEQ ID NO:227, respectively. The corresponding coding DNA sequences are set forth in SEQ ID NO:237 and SEQ ID NO:238, respectively. Further included are nucleic acid sequences hybridizing to SEQ ID NO:228 or SEQ ID NOs:235-238 or encoding a′ protein at least 70%, 75%, 80%, 85%, 90%, 95%, 98% identical to SEQ ID NO:205 or SEQ ID NOs:224-227.

(C) Full-length plant DP and plant E2F proteins or corresponding DNA sequences may also be used to modify said E2F/DP-related processes. Furthermore, plant DP and plant E2F proteins or corresponding DNA sequences, or parts thereof, can be used either separately or in combination to modify said E2F/DP-related processes. This is underscored by the demonstration that AtDPs and AtE2Fs are co-expressed in actively dividing cells and in at least some plant tissues (Example 13 and FIGS. 57 and 58).

Various aspects of the invention are described in further detail in the following subsections:

I. Isolated Nucleic Acid Molecules

One aspect of the invention pertains to isolated nucleic acid molecules that encode CCP proteins or biologically active portions thereof, as well as nucleic acid fragments sufficient for use as hybridization probes to identify CCP-encoding nucleic acids (e.g., CCP mRNA) and fragments for use as PCR primers for the amplification or mutation of CCP nucleic acid molecules. As used herein, the term “nucleic acid molecule” is intended to include DNA molecules (e.g., cDNA or genomic DNA) and RNA molecules (e.g., mRNA) and analogs of the DNA or RNA generated using nucleotide analogs. The nucleic acid molecule can be single-stranded or double-stranded, but preferably is double-stranded DNA.

An “isolated” nucleic acid molecule is one which is separated from other nucleic acid molecules which are present in the natural source of the nucleic acid. For example, with regards to genomic DNA, the term “isolated” includes nucleic acid molecules which are separated from the chromosome with which the genomic DNA is naturally associated. Preferably, an “isolated” nucleic acid is free of sequences which naturally flank the nucleic acid (i.e., sequences located at the 5′ and 3′ ends of the nucleic acid) in the genomic DNA of the organism from which the nucleic acid is derived. For example, in various embodiments, the isolated CCP nucleic acid molecule can contain less than about 5 kb, 4 kb, 3 kb, 2 kb, 1 kb, 0.5 kb or 0.1 kb of nucleotide sequences which naturally flank the nucleic acid molecule in genomic DNA of the cell from which the nucleic acid is derived. Moreover, an “isolated” nucleic acid molecule, such as a cDNA molecule, can be substantially free of other cellular material, or culture medium when produced by recombinant techniques, or substantially free of chemical precursors or other chemicals when chemically synthesized.

A nucleic acid molecule of the present invention, e.g., a nucleic acid molecule having the nucleotide sequence of SEQ ID NO:1-66 or 228-239, or a portion thereof, can be isolated using standard molecular biology techniques and the sequence information provided herein. For example, using all or portion of the nucleic acid sequence of SEQ ID NO:1-66 or 228-239, as a hybridization probe, CCP nucleic acid molecules can be isolated using standard hybridization and cloning techniques (e.g., as described in Sambrook, J., Fritsh, E. F., and Maniatis, T. Molecular Cloning: A Laboratory Manual. 2nd, ed., Cold Spring Harbor Laboratory, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1989).

Moreover, a nucleic acid molecule encompassing all or a portion of SEQ ID NO:1-66 or 228-239 can be isolated by the polymerase chain reaction (PCR) using synthetic oligonucleotide primers designed based upon the sequence of SEQ ID NO:1-66 or 228-239, respectively.

A nucleic acid of the invention can be amplified using cDNA, mRNA or alternatively, genomic DNA, as a template and appropriate oligonucleotide primers according to standard PCR amplification techniques. The nucleic acid so amplified can be cloned into an appropriate vector and characterized by DNA sequence analysis.

Furthermore, oligonucleotides corresponding to CCP nucleotide sequences can be prepared by standard synthetic techniques, e.g., using an automated DNA synthesizer.

In a preferred embodiment, an isolated nucleic acid molecule of the invention comprises the nucleotide sequence shown in SEQ ID NO:1-66 or 228-239.

In another preferred embodiment, an isolated nucleic acid molecule of the invention comprises a nucleic acid molecule which is a complement of the nucleotide sequence shown in SEQ ID NO:1-66 or 228-239, or a portion of any of these nucleotide sequences. A nucleic acid molecule which is complementary to the nucleotide sequence shown in SEQ ID NO:1-66 or 228-239, is one which is sufficiently complementary to the nucleotide sequence shown in SEQ ID NO:1-66 or 228-239, respectively, such that it can hybridize to the nucleotide sequence shown in SEQ ID NO:1-66 or 228-239, respectively, thereby forming a stable duplex.

In still another preferred embodiment, an isolated nucleic acid molecule of the present invention comprises a nucleotide sequence which is at least about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98% or more homologous to the nucleotide sequence (e.g., to the entire length of the nucleotide sequence) shown in SEQ ID NO:1-66 or 228-239, or a portion of any of these nucleotide sequences.

Moreover, the nucleic acid molecule of the invention can comprise only a portion of the nucleic acid sequence of SEQ ID NO:1-66 or 228-239, for example a fragment which can be used as a probe or primer or a fragment encoding a biologically active portion of a CCP protein. The nucleotide sequence determined from the cloning of the CCP gene allows for the generation of probes and primers designed for use in identifying and/or cloning other CCP family members, as well as CCP homologues from other species. The probe/primer typically comprises substantially purified oligonucleotide. The oligonucleotide typically comprises a region of nucleotide sequence that hybridizes under stringent conditions to at least about 12 or 15, preferably about 20 or 25, more preferably about 30, 35, 40, 45, 50, 55, 60, 65, or 75 consecutive nucleotides of a sense sequence of SEQ ID NO:1-66 or 228-239, or of a naturally occurring allelic variant or mutant of SEQ ID NO:1-66 or 228-239. In an exemplary embodiment, a nucleic acid molecule of the present invention comprises a nucleotide sequence which is at least 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, or 800 nucleotides in length and hybridizes under stringent hybridization conditions to a nucleic acid molecule of SEQ ID NO:1-66 or 228-239.

Probes based on the CCP nucleotide sequences can be used to detect transcripts or genomic sequences encoding the same or homologous proteins. In preferred embodiments, the probe further comprises a label group attached thereto, e.g., the label group can be a radioisotope, a fluorescent compound, an enzyme, or an enzyme co-factor. Such probes can be used as a part of a diagnostic test kit for identifying cells or tissues which misexpress a CCP protein, such as by measuring a level of a CCP-encoding nucleic acid in a sample of cells from a subject e.g., detecting CCP mRNA levels or determining whether a genomic CCP gene has been mutated or deleted.

A nucleic acid fragment encoding a “biologically active portion of a CCP protein” can be prepared by isolating a portion of the nucleotide sequence of SEQ ID NO:1-66 or 228-239, which encodes a polypeptide having a CCP biological activity (the biological activities of the CCP proteins are described herein), expressing the encoded portion of the CCP protein (e.g., by recombinant expression in vitro) and assessing the activity of the encoded portion of the CCP protein.

The invention further encompasses nucleic acid molecules that differ from the nucleotide sequence shown in SEQ ID NO:1-66 or 228-239, due to the degeneracy of the genetic code and, thus, encode the same CCP proteins as those encoded by the nucleotide sequence shown in SEQ ID NO:1-66 or 228-239. In another embodiment, an isolated nucleic acid molecule of the invention has a nucleotide sequence encoding a CCP protein.

In addition to the CCP nucleotide sequences shown in SEQ ID NO:1-66 or 228-239, it will be appreciated by those skilled in the art that DNA sequence polymorphisms that lead to changes in the amino acid sequences of the CCP proteins may exist within a population (e.g., an Arabidopsis or rice plant population). Such genetic polymorphism in the CCP genes may exist among individuals within a population due to natural allelic variation. As used herein, the terms “gene” and “recombinant gene” refer to nucleic acid molecules which include an open reading frame encoding an CCP protein, preferably a plant CCP protein, and can further include non-coding regulatory sequences, and introns. Such natural allelic variations include both functional and non-functional CCP proteins and can typically result in 1-5% variance in the nucleotide sequence of a CCP gene. Any and all such nucleotide variations and resulting amino acid polymorphisms in CCP genes that are the result of natural allelic variation and that do not alter the functional activity of a CCP protein are intended to be within the scope of the invention. Differences in preferred codon usage are illustrated below for Agrobacterium tumefaciens (a bacterium), Arabidopsis thaliana, Medicago sativa (two dicotyledonous plants) and Oryza sativa (a monocotyledonous plant). These examples were extracted from http://www.kazusa.or.jp/codon. For example, the codon GGC (for glycine) is the most frequently used codon in A. tumefaciens (36.2%), is the second most frequently used codon in O. sativa but is used at much lower frequencies in A. thaliana and M. sativa (9% o and 8.4%, respectively). Of the four possible codons encoding glycine the GGC codon is most preferably used in A. tumefaciens and O. sativa. However, in A. thaliana the GGA (and GGU) codon is most preferably used, whereas in M. sativa the GGU (and GGA) codon is most preferably used.

Moreover, nucleic acid molecules encoding other CCP family members and, thus, which have a nucleotide sequence which differs from the CCP sequences of SEQ ID NO:1-66 or 228-239 are intended to be within the scope of the invention. For example, another CCP cDNA can be identified based on the nucleotide sequence of the plant CCP molecules described herein. Moreover, nucleic acid molecules encoding CCP proteins from different species, and thus which have a nucleotide sequence which differs from the CCP sequences of SEQ ID NO:1-66 or 228-239 are intended to be within the scope of the invention. For example, a human CCP cDNA can be identified based on the nucleotide sequence of a plant CCP.

Nucleic acid molecules corresponding to natural allelic variants and homologues of the CCP cDNAs of the invention can be isolated based on their homology to the CCP nucleic acids disclosed herein using the cDNAs disclosed herein, or a portion thereof; as a hybridization probe according to standard hybridization techniques under stringent hybridization conditions.

Accordingly, in another embodiment, an isolated nucleic acid molecule of the invention is at least 15, 20, 25, 30 or more nucleotides in length and hybridizes under stringent conditions to the nucleic acid molecule comprising the nucleotide sequence of SEQ ID NO:1-66 or 228-239. In other embodiment, the nucleic acid is at least 30, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, or 600 nucleotides in length. As used herein, the term “hybridizes under stringent conditions” is intended to describe conditions for hybridization and washing under which nucleotide sequences at least 30%, 40%, 50%, or 60% homologous to each other typically remain hybridized to each other. Preferably, the conditions are such that sequences at least about 70%, more preferably at least about 80%, even more preferably at least about 85% or 90% homologous to each other typically remain hybridized to each other. Such stringent conditions are known to those skilled in the art and can be found in Current Protocols in Molecular Biology, John Wiley & Sons, N.Y. (1989), 6.3.1-6.3.6. A preferred, non-limiting example of stringent hybridization conditions are hybridization in 6× sodium chloride/sodium citrate (SSC) at about 45° C., followed by one or more washes in 0.2×SSC, 0.1% SDS at about 45° C., followed by one or more washes in 0.2×SSC, 0.1% SDS at 50° C., preferably at 55° C., more preferably at 60° C., and even more preferably at 65° C. Ranges intermediate to the above-recited values, e.g., at 60-65° C. or at 55-60° C. are also intended to be encompassed by the present invention. Preferably, an isolated nucleic acid molecule of the invention that hybridizes under stringent conditions to the sequence of SEQ ID NO:1-66 or 228-239 corresponds to a naturally-occurring nucleic acid molecule. As used herein, a “naturally-occurring” nucleic acid molecule refers to an RNA or DNA molecule having a nucleotide sequence that occurs in nature (e.g., encodes a natural protein).

In addition to naturally-occurring allelic variants of the CCP sequences that may exist in nature, the skilled artisan will further appreciate that changes can be introduced by mutation into the nucleotide sequences of SEQ ID NO:1-66 or 228-239, thereby leading to changes in the amino acid sequence of the encoded CCP proteins, without altering the functional ability of the CCP proteins. For example, nucleotide substitutions leading to amino acid substitutions at “non-essential” amino acid residues can be made in the sequence of a CCP protein. A “non-essential” amino acid residue is a residue that can be altered from the wild-type sequence of CCP without altering the biological activity, whereas an “essential” amino acid residue is required for biological activity. For example, amino acid residues that are conserved among the CCP proteins of the present invention, are predicted to be particularly unamenable to alteration. Furthermore, additional amino acid residues that are conserved between the CCP proteins of the present invention and other CCP family members are not likely to be amenable to alteration.

Accordingly, another aspect of the invention pertains to nucleic acid molecules encoding CCP proteins that contain changes in amino acid residues that are not essential for activity.

An isolated nucleic acid molecule encoding a CCP protein homologous to the CCP proteins of the present invention can be created by introducing one or more nucleotide substitutions, additions or deletions into the nucleotide sequence of SEQ ID NO:1-66 or 228-239, such that one or more amino acid substitutions, additions or deletions are introduced into the encoded protein. Mutations can be introduced into SEQ ID NO:1-66 or 228-239 by standard techniques, such as site-directed mutagenesis and PCR-mediated mutagenesis. Preferably, conservative amino acid substitutions are made at one or more predicted non-essential amino acid residues. A “conservative amino acid substitution” is one in which the amino acid residue is replaced with an amino acid residue having a similar side chain. Families of amino acid residues having similar side chains have been defined in the art. These families include amino acids with basic side chains (e.g., lysine, arginine, histidine), acidic side chains (e.g., aspartic acid, glutamic acid), uncharged polar side chains (e.g., glycine, asparagine, glutamine, serine, threonine, tyrosine, cysteine), nonpolar side chains (e.g., alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, tryptophan), beta-branched side chains (e.g., threonine, valine, isoleucine) and aromatic side chains (e.g., tyrosine, phenylalanine, tryptophan, histidine). Thus, a predicted nonessential amino acid residue in a CCP protein is preferably replaced with another amino acid residue from the same side chain family. Alternatively, in another embodiment, mutations can be introduced randomly along all or part of a CCP coding sequence, such as by saturation mutagenesis, and the resultant mutants can be screened for CCP biological activity to identify mutants that retain activity. Following mutagenesis of SEQ ID NO:1-66 or 228-239, the encoded protein can be expressed recombinantly and the activity of the protein can be determined. Another alternative embodiment comprises targeted in vivo gene correction or modification which can be achieved by chimeric RNA/DNA oligonucleotides (e.g., Yoon et al. (1996), Proc. Natl. Acad. Sci. USA 93, 2071-2076; Arntzen et al. (1999) WO99/07865).

In a preferred embodiment, a mutant CCP protein can be assayed for the ability to: (1) regulate transmission of signals from cellular receptors, e.g. hormone receptors; (2) control cell cycle checkpoints, e.g. entry of cells into mitosis; (3) modulate the cell cycle; (4) modulate cell death, e.g., apoptosis; (5) modulate cytoskeleton function, e.g. actin bundling; (6) phosphorylate a substrate; (7) create dominant negative or dominant positive effects in transgenic plants; (8) interact with other cell cycle control proteins in, e.g. a yeast two hybrid assay; (9) modulate CDK activity (e.g., cyclin-CDK activity); (10) regulate cyclin-CDK complex assembly; (11) regulate the commitment of cells to divide, e.g., by integrating mitogenic and antimitogenic signals; (12) regulate cell cycle progression; (13) regulate DNA replication and/or DNA repair; (14) modulate gene transcription, e.g., regulate E2F/DP-dependent transcription of genes; (15) regulate cyclin degradation; (16) modulate cell cycle withdrawal and/or cell differentiation; (17) control organ (e.g., plant organ) and/or organism (e.g., plant organism) size; (18) control organ (e.g., plant organ) and/or organism (e.g., plant organism) growth or growth rate; and (19) regulate endoreduplication.

In addition to the nucleic acid molecules encoding CCP proteins described above, another aspect of the invention pertains to isolated nucleic acid molecules which are antisense thereto. An “antisense” nucleic acid comprises a nucleotide sequence which is complementary to a “sense” nucleic acid encoding a protein, e.g., complementary to the coding strand of a double-stranded cDNA molecule or complementary to an mRNA sequence. Accordingly, an antisense nucleic acid can hydrogen bond to a sense nucleic acid. The antisense nucleic acid can be complementary to an entire CCP coding strand, or only to a portion thereof. In one embodiment, an antisense nucleic acid molecule is antisense to a “coding region” of the coding strand of a nucleotide sequence encoding CCP. The term “coding region” refers to the region of the nucleotide sequence comprising codons which are translated into amino acid residues. In another embodiment, the antisense nucleic acid molecule is antisense to a “noncoding region” of the coding strand of a nucleotide sequence encoding CCP. The term “noncoding region” refers to 5′ and 3′ sequences which flank the coding region that are not translated into amino acids (i.e., also referred to as 5′ and 3′ untranslated regions).

Given the coding strand sequences encoding CCP disclosed herein, antisense nucleic acids of the invention can be designed according to the rules of Watson and Crick base pairing. The antisense nucleic acid molecule can be complementary to the entire coding region of CCP mRNA, but more preferably is an oligonucleotide which is antisense to only a portion of the coding or noncoding region of CCP mRNA. For example, the antisense oligonucleotide can be complementary to the region surrounding the translation start site of CCP mRNA. An antisense oligonucleotide can be, for example, about 5, 10, 15, 20, 25, 30, 35, 40, 45 or 50 nucleotides in length. An antisense nucleic acid of the invention can be constructed using chemical synthesis and enzymatic ligation reactions using procedures known in the art. For example, an antisense nucleic acid (e.g., an antisense oligonucleotide) can be chemically synthesized using naturally occurring nucleotides or variously modified nucleotides designed to increase the biological stability of the molecules or to increase the physical stability of the duplex formed between the antisense and sense nucleic acids, e.g., phosphorothioate derivatives and acridine substituted nucleotides can be used. Examples of modified nucleotides which can be used to generate the antisense nucleic acid include 5-fluorouracil, 5-bromouracil, 5-chlorouracil, 5-iodouracil, hypoxanthine, xantine, 4-acetylcytosine, 5-(carboxyhydroxylmethyl)uracil, 5-carboxymethylaminomethyl-2-thiouridine, 5-carboxymethylaminomethyluracil, dihydrouracil, beta-D-galactosylqueosine, inosine, N6-isopentenyladenine, 1-methylguanine, 1-methylinosine, 2,2-dimethylguanine, 2-methyladenine, 2-methylguanine, 3-methylcytosine, 5-methylcytosine, N6-adenine, 7-methylguanine, 5-methylaminomethyluracil, 5-methoxyaminomethyl-2-thiouracil, beta-D-mannosylqueosine, 5′-methoxycarboxymethyluracil, 5-methoxyuracil, 2-methylthio-N6-isopentenyladenine, uracil-5-oxyacetic acid (v), wybutoxosine, pseudouracil, queosine, 2-thiocytosine, 5-methyl-2-thiouracil, 2-thiouracil, 4-thiouracil, 5-methyluracil, uracil-5-oxyacetic acid methylester, uracil-5-oxyacetic acid (v), 5-methyl-2-thiouracil, 3-(3-amino-3-N-2-carboxypropyl)uracil, (acp3)w, and 2,6-diaminopurine. Alternatively, the antisense nucleic acid can be produced biologically using an expression vector into which a nucleic acid has been subcloned in an antisense orientation (i.e., RNA transcribed from the inserted nucleic acid will be of an antisense orientation to a target nucleic acid of interest, described further in the following subsection). Preferably, production of antisense nucleic acids in plants occurs by means of a stably integrated transgene comprising a promoter operative in plants, an antisense oligonucleotide, and a terminator.

Other known nucleotide modifications include methylation, cyclization and ‘caps’ and substitution of one or more of the naturally occurring nucleotides with an analog such as inosine. Modifications of nucleotides include modifications generated by the addition to nucleotides of acridine, amine, biotin, cascade blue, cholesterol, Cy3®, Cy5®, Cy5.5® Dabcyl, digoxigenin, dinitrophenyl, Edam, 6-FAM, fluorescein, 3′-glyceryl, HEX, IRD-700, IRD-800, JOE, phosphate psoralen, rhodamine, ROX, thiol (SH), spacers, TAMRA, TET, AMCA-S®, SE, BODIPY®, Marina Blue®, Pacific Blue®, Oregon Green®, Rhodamine Green®, Rhodamine Red®, Rhodol Green® and Texas Red®. Polynucleotide backbone modifications include methylphosphonate, 2′-OMe-methylphosphonate RNA, phosphorothiorate, RNA, 2′-OMeRNA. Base modifications include 2-amino-dA, 2-aminopurine, 3′-(ddA), 3′ dA(cordycepin), 7-deaza-dA, 8-Br-dA, 8-oxo-dA, N⁶-Me-dA, abasic site (dSpacer), biotin dT, T-OMe-5Me-C, 2′-OMe-propynyl-C, 3′-(5-Me-dC), 3′-(ddC), 5-Br-dC, 5-I -dC, 5-Me-dC, 5-F-dC, carboxy-dT, convertible dA, convertible dC, convertible dG, convertible dT, convertible dU, 7-deaza-dG, 8-Br-dG, 8-oxo-dG, O⁶-Me-dG, S6-DNP-dG, 4-methyl-indole, 5-nitroindole, 2′-OMe-inosine, 2′-dI, O⁶-phenyl-dI, 4-methyl-indole, 2′-deoxynebularine, 5-nitroindole, 2-aminopurine, dP(purine analogue), dK(pyrimidine analogue), 3-nitropyrrole, 2-thio-dT, 4-thio-dT, biotin-dT, carboxy-dT, O⁴-Me-dT, O⁴-triazol dT, 2′-OMe-propynyl-U, 5-Br-dU, 2′-dU, 5-F-dU, 5-I-dU, O⁴-triazol dU.

The antisense nucleic acid molecules of the invention are typically introduced into a plant or administered to a subject or generated in situ such that they hybridize with or bind to cellular mRNA and/or genomic DNA encoding a CCP protein to thereby inhibit expression of the protein, e.g., by inhibiting transcription and/or translation. The hybridization can be by conventional nucleotide complementarity to form a stable duplex, or, for example, in the case of an antisense nucleic acid molecule which binds to DNA duplexes, through specific interactions in the major groove of the double helix. An example of a route of introduction or administration of antisense nucleic acid molecules of the invention include transformation in a plant or direct injection at a tissue site in a subject. Alternatively, antisense nucleic acid molecules can be modified to target selected cells and then administered systemically. For example, for systemic administration, antisense molecules can be modified such that they specifically bind to receptors or antigens expressed on a selected cell surface, e.g., by linking the antisense nucleic acid molecules to peptides or antibodies which bind to cell surface receptors or antigens. The antisense nucleic acid molecules can also be delivered to cells using the vectors described herein. To achieve sufficient intracellular concentrations of the antisense molecules, vector constructs in which the antisense nucleic acid molecule is placed under the control of a constitutive promoter or a strong pol II or pol III promoter are preferred.

In yet another embodiment, the antisense nucleic acid molecule of the invention is an α-anomeric nucleic acid molecule. An α-anomeric nucleic acid molecule forms specific double-stranded hybrids with complementary RNA in which, contrary to the usual β-units, the strands run parallel to each other (Gaultier et al. (1987) Nucleic Acids. Res. 15:6625-6641). The antisense nucleic acid molecule can also comprise a 2′-o-methylribonucleotide (Inoue et al. (1987) Nucleic Acids Res. 15:6131-6148) or a chimeric RNA-DNA analogue (Inoue et al. (1987) FEBS Lett. 215:327-330).

In another embodiment, the antisense nucleic acid molecule further comprises a sense nucleic acid molecule complementary to the antisense nucleic acid molecule. Gene silencing methods based on such nucleic acid molecules are well known to the skilled artisan (e.g., Grierson et al. (1998) WO 98/53083; Waterhouse et al. (1999) WO 99/53050).

In still another embodiment, an antisense nucleic acid of the invention is a ribozyme. Ribozymes are catalytic RNA molecules with ribonuclease activity which are capable of cleaving a single-stranded nucleic acid, such as an mRNA, to which they have a complementary region. Thus, ribozymes (e.g., hammerhead ribozymes (described in Haselhoff and Gerlach (1988) Nature 334:585-591)) can be used to catalytically cleave CCP mRNA transcripts to thereby inhibit translation of CCP mRNA. A ribozyme having specificity for a CCP-encoding nucleic acid can be designed based upon the nucleotide sequence of a CCP cDNA disclosed herein (i.e., SEQ ID NO:1-66 or 228-239). For example, a derivative of a Tetrahymena L-19 IVS RNA can be constructed in which the nucleotide sequence of the active site is complementary to the nucleotide sequence to be cleaved in a CCP-encoding mRNA. See, e.g., Cech et al. U.S. Pat. No. 4,987,071; and Cech et al. U.S. Pat. No. 5,116,742. Alternatively, CCP mRNA can be used to select a catalytic RNA having a specific ribonuclease activity from a pool of RNA molecules. See, e.g., Bartel, D. and Szostak, J. W. (1993) Science 261:1411-1418.

The use of ribozymes for gene silencing in plants is known in the art (e.g., Atkins et al. (1994) WO 94/00012; Lenne et al. (1995) WO 95/03404; Lutziger et al. (2000) WO 00/00619; Prinsen et al. (1997) WO 97/13865 and Scott et al. (1997) WO/97/38116).

Alternatively, CCP gene expression can be inhibited by targeting nucleotide sequences complementary to the regulatory region of the CCP (e.g., the CCP promoter and/or enhancers) to form triple helical structures that prevent transcription of the CCP gene in target cells. See generally, Helene, C. (1991) Anticancer Drug Des. 6(6):569-84; Helene, C. et al. (1992) Ann. N.Y. Acad. Sci. 660:27-36; and Maher, L. J. (1992) Bioassays 14(12):807-15.

In yet another embodiment, the CCP nucleic acid molecules of the present invention can be modified at the base moiety, sugar moiety or phosphate backbone to improve, e.g., the stability, hybridization, or solubility of the molecule. For example, the deoxyribose phosphate backbone of the nucleic acid molecules can be modified to generate peptide nucleic acids (see Hyrup B. et al. (1996) Bioorganic & Medicinal Chemistry 4 (1): 5-23). As used herein, the terms “peptide nucleic acids” or “PNAs” refer to nucleic acid mimics, e.g., DNA mimics, in which the deoxyribose phosphate backbone is replaced by a pseudopeptide backbone and only the four natural nucleobases are retained. The neutral backbone of PNAs has been shown to allow for specific hybridization to DNA and RNA under conditions of low ionic strength. The synthesis of PNA oligomers can be performed using standard solid phase peptide synthesis protocols as described in Hyrup B. et al. (1996) supra; Perry-O'Keefe et al. Proc. Natl. Acad. Sci. 93: 14670-675.

PNAs of CCP nucleic acid molecules can be used for increasing crop yield in plants or in therapeutic and diagnostic applications. For example, PNAs can be used as antisense or antigene agents for sequence-specific modulation of gene expression by, for example, inducing transcription or translation arrest or inhibiting replication. PNAs of CCP nucleic acid molecules can also be used in the analysis of single base pair mutations in a gene, (e.g., by PNA-directed PCR clamping); as ‘artificial restriction enzymes’ when used in combination with other enzymes, (e.g., S1 nucleases (Hyrup B. (1996) supra)); or as probes or primers for DNA sequencing or hybridization (Hyrup B. et al. (1996) supra; Perry-O'Keefe supra).

In another embodiment, PNAs of CCP can be modified, (e.g., to enhance their stability or cellular uptake), by attaching lipophilic or other helper groups to PNA, by the formation of PNA-DNA chimeras, or by the use of liposomes or other techniques of drug delivery known in the art. For example, PNA-DNA chimeras of CCP nucleic acid molecules can be generated which may combine the advantageous properties of PNA and DNA. Such chimeras allow DNA recognition enzymes, (e.g., RNAse H and DNA polymerases), to interact with the DNA portion while the PNA portion would provide high binding affinity and specificity. PNA-DNA chimeras can be linked using linkers of appropriate lengths selected in terms of base stacking, number of bonds between the nucleobases, and orientation (Hyrup B. (1996) supra). The synthesis of PNA-DNA chimeras can be performed as described in Hyrup B. (1996) supra and Finn P. J. et al. (1996) Nucleic Acids Res. 24 (17): 3357-63. For example, a DNA chain can be synthesized on a solid support using standard phosphoramidite coupling chemistry and modified nucleoside analogs, e.g., 5′-(4-methoxytrityl)amino-5′-deoxy-thymidine phosphoramidite, can be used as a between the PNA and the 5′ end of DNA (Mag, M. et al. (1989) Nucleic Acid Res. 17: 5973-88). PNA monomers are then coupled in a stepwise manner to produce a chimeric molecule with a 5′ PNA segment and a 3′ DNA segment (Finn P. J. et al. (1996) supra). Alternatively, chimeric molecules can be synthesized with a 5′ DNA segment and a 3′ PNA segment (Peterser, K. H. et al. (1975) Bioorganic Med. Chem. Lett. 5: 1119-11124).

In other embodiments, the oligonucleotide may include other appended groups such as peptides (e.g., for targeting host cell receptors in vivo), or agents facilitating transport across the cell membrane (see, e.g., Letsinger et al. (1989) Proc. Natl. Acad. Sci. US. 86:6553-6556; Lemaitre et al. (1987) Proc. Natl. Acad. Sci. USA 84:648-652; PCT Publication No. WO88/09810) or the blood-brain barrier (see, e.g., PCT Publication No. WO89/10134). In addition, oligonucleotides can be modified with hybridization-triggered cleavage agents (See, e.g., Krol et al. (1988) Bio-Techniques 6:958-976) or intercalating agents. (See, e.g., Zon (1988) Pharm. Res. 5:539-549). To this end, the oligonucleotide may be conjugated to another molecule, (e.g., a peptide, hybridization triggered cross-linking agent, transport agent, or hybridization-triggered cleavage agent).

II. Isolated CCP Proteins and Anti-CCP Antibodies

One aspect of the invention pertains to isolated CCP proteins (e.g., the amino acid sequences set forth in SEQ ID NO:67-132, 205, 211, 215-216, or 220-227) and biologically active portions thereof, as well as polypeptide fragments suitable for use as immunogens to raise anti-CCP antibodies. In one embodiment, native CCP proteins can be isolated from cells or tissue sources by an appropriate purification scheme using standard protein purification techniques. In another embodiment, CCP proteins are produced by recombinant DNA techniques. Alternative to recombinant expression, a CCP protein or polypeptide can be synthesized chemically using standard peptide synthesis techniques.

An “isolated” or “purified” protein or biologically active portion thereof is substantially free of cellular material or other contaminating proteins from the cell or tissue source from which the CCP protein is derived, or substantially free from chemical precursors or other chemicals when chemically synthesized. The language “substantially free of cellular material” includes preparations of CCP protein in which the protein is separated from cellular components of the cells from which it is isolated or recombinantly produced. In one embodiment, the language “substantially free of cellular material” includes preparations of CCP protein having less than about 30% (by dry weight) of non-CCP protein (also referred to herein as a “contaminating protein”), more preferably less than about 20% of non-CCP protein, still more preferably less than about 10% of non-CCP protein, and most preferably less than about 5% non-CCP protein. When the CCP protein or biologically active portion thereof is recombinantly produced, it is also preferably substantially free of culture medium, i.e., culture medium represents less than about 20%, more preferably less than about 10%, and most preferably less than about 5% of the volume of the protein preparation.

The language “substantially free of chemical precursors or other chemicals” includes preparations of CCP protein in which the protein is separated from chemical precursors or other chemicals which are involved in the synthesis of the protein. In one embodiment, the language “substantially free of chemical precursors or other chemicals” includes preparations of CCP protein having less than about 30% (by dry weight) of chemical precursors or non-CCP chemicals, more preferably less than about 20% chemical precursors or non-CCP chemicals, still more preferably less than about 10% chemical precursors or non-CCP chemicals, and most preferably less than about 5% chemical precursors or non-CCP chemicals.

Biologically active portions of a CCP protein include peptides comprising amino acid sequences sufficiently homologous to or derived from the amino acid sequence of the CCP protein, which include less amino acids than the full length CCP proteins, and exhibit at least one activity of a CCP protein. Typically, biologically active portions comprise a domain or motif with at least one activity of the CCP protein. A biologically active portion of a CCP protein can be a polypeptide which is, for example, at least 10, 25, 50, 100 or more amino acids in length.

To determine the percent identity of two amino acid sequences or of two nucleic acid sequences, the sequences are aligned for optimal comparison purposes (e.g., gaps can be introduced in one or both of a first and a second amino acid or nucleic acid sequence for optimal alignment and non-homologous sequences can be disregarded for comparison purposes). In a preferred embodiment, the length of a reference sequence aligned for comparison purposes is at least 30%, preferably at least 40%, more preferably at least 50%, even more preferably at least 60%, and even more preferably at least 70%, 80%, or 90% of the length of the reference sequence. The amino acid residues or nucleotides at corresponding amino acid positions or nucleotide positions are then compared. When a position in the first sequence is occupied by the same amino acid residue or nucleotide as the corresponding position in the second sequence, then the molecules are identical at that position (as used herein amino acid or nucleic acid “identity” is equivalent to amino acid or nucleic acid “homology”). The percent identity between the two sequences is a function of the number of identical positions shared by the sequences, taking into account the number of gaps, and the length of each gap, which need to be introduced for optimal alignment of the two sequences.

The comparison of sequences and determination of percent identity between two sequences can be accomplished using a mathematical algorithm. In a preferred embodiment, the percent identity between two amino acid sequences is determined using the Needleman and Wunsch (J. Mol. Biol. (48):444-453 (1970)) algorithm which has been incorporated into the GAP program in the GCG software package (available at http://www.gcg.com), using either a Blosum 62 matrix or a PAM250 matrix, and a gap weight of 16, 14, 12, 10, 8, 6, or 4 and a length weight of 1, 2, 3, 4, 5, or 6. In yet another preferred embodiment, the percent identity between two nucleotide sequences is determined using the GAP program in the GCG software package (available at http://www.gcg.com), using a NWSgapdna.CMP matrix and a gap weight of 40, 50, 60, 70, or 80 and a length weight of 1, 2, 3, 4, 5, or 6. A preferred, non-limiting example of parameters to be used in conjunction with the GAP program include a Blosum 62 scoring matrix with a gap penalty of 12, a gap extend penalty of 4, and a frameshift gap penalty of 5.

In another embodiment, the percent identity between two amino acid or nucleotide sequences is determined using the algorithm of E. Meyers and W. Miller (Comput. Appl. Biosci., 4:11-17 (1988)) which has been incorporated into the ALIGN program (version 2.0 or version 2.0U), using a PAM120 weight residue table, a gap length penalty of 12 and a gap penalty of 4.

The nucleic acid and polypeptide sequences of the present invention can further be used as a “query sequence” to perform a search against public databases to, for example, identify other family members or related sequences. Such searches can be performed using the NBLAST and XBLAST programs (version 2.0) of Altschul, et al. (1990) J. Mol. Biol. 215:403-10. BLAST nucleotide searches can be performed with the NBLAST program, score=100, wordlength=12 to obtain nucleotide sequences homologous to Kinase and Phosphatase nucleic acid molecules of the invention. BLAST protein searches can be performed with the XBLAST program, score=100, wordlength=3, and a Blosum62 matrix to obtain amino acid sequences homologous to Kinase and Phosphatase polypeptide molecules of the invention. To obtain gapped alignments for comparison purposes, Gapped BLAST can be utilized as described in Altschul et al., (1997) Nucleic Acids Res. 25(17):3389-3402. When utilizing BLAST and Gapped BLAST programs, the default parameters of the respective programs (e.g., XBLAST and NBLAST) can be used. See http://www.ncbi.nlm.nih.gov.

The invention also provides CCP chimeric or fusion proteins. As used herein, a CCP “chimeric protein” or “fusion protein” comprises a CCP polypeptide operatively linked to a non-CCP polypeptide. An “CCP polypeptide” refers to a polypeptide having an amino acid sequence corresponding to CCP, whereas a “non-CCP polypeptide” refers to a polypeptide having an amino acid sequence corresponding to a protein which is not substantially homologous to the CCP protein, e.g., a protein which is different from the CCP protein and which is derived from the same or a different organism. Within a CCP fusion protein the CCP polypeptide can correspond to all or a portion of a CCP protein. In a preferred embodiment, a CCP fusion protein comprises at least one biologically active portion of a CCP protein. In another preferred embodiment, a CCP fusion protein comprises at least two biologically active portions of a CCP protein. Within the fusion protein, the term “operatively linked” is intended to indicate that the CCP polypeptide and the non-CCP polypeptide are fused in-frame to each other. The non-CCP polypeptide can be fused to the N-terminus or C-terminus of the CCP polypeptide or can be inserted within the CCP polypeptide. The non-CCP polypeptide can, for example, be (histidine)₆-tag, glutathione S-transferase, protein A, maltose-binding protein, dihydrofolate reductase, Tag•100 epitope (EETARFQPGYRS; SEQ ID NO:199), c-myc epitope (EQKLISEEDL; SEQ ID NO:200), FLAG®-epitope (DYKDDDK; SEQ ID NO:201), lacZ, CMP (calmodulin-binding peptide), HA epitope (YPYDVPDYA; SEQ ID NO:202), protein C epitope (EDQVDPRLIDGK; SEQ ID NO:203) or VSV epitope (YTDIEMNRLGK; SEQ ID NO:204).

For example, in one embodiment, the fusion protein is a GST-CCP fusion protein in which the CCP sequences are fused to the C-terminus of the GST sequences. Such fusion proteins can facilitate the purification of recombinant CCP.

In another embodiment, the fusion protein is a CCP protein containing a heterologous signal sequence at its N-terminus. In certain host cells (e.g., plant or mammalian host cells), expression and/or secretion of CCP can be increased through use of a heterologous signal sequence.

The CCP fusion proteins of the invention can be incorporated into pharmaceutical compositions and administered to a plant or a subject in vivo. The CCP fusion proteins can be used to affect the bioavailability of a CCP substrate. Use of CCP fusion proteins may be useful agriculturally for the increase of crop yields or therapeutically for the treatment of cellular growth related disorders, e.g., cancer. Moreover, the CCP-fusion proteins of the invention can be used as immunogens to produce anti-CCP antibodies in a subject, to purify CCP ligands and in screening assays to identify molecules which inhibit the interaction of CCP with a CCP substrate, e.g., a kinase such as CDC2b.

Preferably, a CCP chimeric or fusion protein of the invention is produced by standard recombinant DNA techniques. For example, DNA fragments coding for the different polypeptide sequences are ligated together in-frame in accordance with conventional techniques, for example by employing blunt-ended or stagger-ended termini for ligation, restriction enzyme digestion to provide for appropriate termini, filling-in of cohesive ends as appropriate, alkaline phosphatase treatment to avoid undesirable joining, and enzymatic ligation. In another embodiment, the fusion gene can be synthesized by conventional techniques including automated DNA synthesizers. Alternatively, PCR amplification of gene fragments can be carried out using anchor primers which give rise to complementary overhangs between two consecutive gene fragments which can subsequently be annealed and reamplified to generate a chimeric gene sequence (see, for example, Current Protocols in Molecular Biology, eds. Ausubel et al. John Wiley & Sons: 1992). Moreover, many expression vectors are commercially available that already encode a fusion moiety (e.g., a GST polypeptide). A CCP-encoding nucleic acid can be cloned into such an expression vector such that the fusion moiety is linked in-frame to the CCP protein.

The present invention also pertains to variants of the CCP proteins which function as either CCP agonists (mimetics) or as CCP antagonists. Variants of the CCP proteins can be generated by mutagenesis, e.g., discrete point mutation or truncation of a CCP protein. An agonist of the CCP proteins can retain substantially the same, or a subset, of the biological activities of the naturally occurring form of a CCP protein. An antagonist of a CCP protein can inhibit one or more of the activities of the naturally occurring form of the CCP protein by, for example, competitively modulating a cellular activity of a CCP protein. Thus, specific biological effects can be elicited by treatment with a variant of limited function. In one embodiment, treatment of a subject with a variant having a subset of the biological activities of the naturally occurring form of the protein has fewer side effects in a subject relative to treatment with the naturally occurring form of the CCP protein.

In one embodiment, variants of a CCP protein which function as either CCP agonists (mimetics) or as CCP antagonists can be identified by screening combinatorial libraries of mutants, e.g., truncation mutants, of a CCP protein for CCP protein agonist or antagonist activity. In one embodiment, a variegated library of CCP variants is generated by combinatorial mutagenesis at the nucleic acid level and is encoded by a variegated gene library. A variegated library of CCP variants can be produced by, for example, enzymatically ligating a mixture of synthetic oligonucleotides into gene sequences such that a degenerate set of potential CCP sequences is expressible as individual polypeptides, or alternatively, as a set of larger fusion proteins (e.g., for phage display) containing the set of CCP sequences therein. There are a variety of methods which can be used to produce libraries of potential CCP variants from a degenerate oligonucleotide sequence. Chemical synthesis of a degenerate gene sequence can be performed in an automatic DNA synthesizer, and the synthetic gene then ligated into an appropriate expression vector. Use of a degenerate set of genes allows for the provision, in one mixture, of all of the sequences encoding the desired set of potential CCP sequences. Methods for synthesizing degenerate oligonucleotides are known in the art (see, e.g., Narang, S. A. (1983) Tetrahedron 39:3; Itakura et al. (1984) Annu. Rev. Biochem. 53:323; Itakura et al. (1984) Science 198:1056; Ike et al. (1983) Nucleic Acid Res. 11:477.

In addition, libraries of fragments of a CCP protein coding sequence can be used to generate a variegated population of CCP fragments for screening and subsequent selection of variants of a CCP protein. In one embodiment, a library of coding sequence fragments can be generated by treating a double stranded PCR fragment of a CCP coding sequence with a nuclease under conditions wherein nicking occurs only about once per molecule, denaturing the double stranded DNA, renaturing the DNA to form double stranded DNA which can include sense/antisense pairs from different nicked products, removing single stranded portions from reformed duplexes by treatment with S1 nuclease, and ligating the resulting fragment library into an expression vector. By this method, an expression library can be derived which encodes N-terminal, C-terminal and internal fragments of various sizes of the CCP protein.

Several techniques are known in the art for screening gene products of combinatorial libraries made by point mutations or truncation, and for screening cDNA libraries for gene products having a selected property. Such techniques are adaptable for rapid screening of the gene libraries generated by the combinatorial mutagenesis of CCP proteins. The most widely used techniques, which are amenable to high through-put analysis, for screening large gene libraries typically include cloning the gene library into replicable expression vectors, transforming appropriate cells with the resulting library of vectors, and expressing the combinatorial genes under conditions in which detection of a desired activity facilitates isolation of the vector encoding the gene whose product was detected. Recrusive ensemble mutagenesis (REM), a new technique which enhances the frequency of functional mutants in the libraries, can be used in combination with the screening assays to identify CCP variants (Arkin and Yourvan (1992) Proc. Natl. Acad. Sci. USA 89:7811-7815; Delgrave et al. (1993) Protein Engineering 6(3):327-331).

In one embodiment, cell based assays can be exploited to analyze a variegated CCP library. For example, a library of expression vectors can be transfected into a cell line which ordinarily synthesizes and secretes CCP. The transfected cells are then cultured such that CCP and a particular mutant CCP are secreted and the effect of expression of the mutant on CCP activity in cell supernatants can be detected, e.g., by any of a number of enzymatic assays. Plasmid DNA can then be recovered from the cells which score for inhibition, or alternatively, potentiation of CCP activity, and the individual clones further characterized.

An isolated CCP protein, or a portion or fragment thereof, can be used as an immunogen to generate antibodies that bind CCP using standard techniques for polyclonal and monoclonal antibody preparation. A full-length CCP protein can be used or, alternatively, the invention provides antigenic peptide fragments of CCP for use as immunogens. The antigenic peptide of CCP comprises at least 8 amino acid residues and encompasses an epitope of CCP such that an antibody raised against the peptide forms a specific immune complex with CCP. Preferably, the antigenic peptide comprises at least 10 amino acid residues, more preferably at least 15 amino acid residues, even more preferably at least 20 amino acid residues, and most preferably at least 30 amino acid residues.

Preferred epitopes encompassed by the antigenic peptide are regions of CCP that are located on the surface of the protein, e.g., hydrophilic regions.

A CCP immunogen typically is used to prepare antibodies by immunizing a suitable subject, (e.g., rabbit, goat, mouse or other mammal) with the immunogen. An appropriate immunogenic preparation can contain, for example, recombinantly expressed CCP protein or a chemically synthesized CCP polypeptide. The preparation can further include an adjuvant, such as Freund's complete or incomplete adjuvant, or similar immunostimulatory agent. Immunization of a suitable subject with an immunogenic CCP preparation induces a polyclonal anti-CCP antibody response.

Accordingly, another aspect of the invention pertains to anti-CCP antibodies. The term “antibody” as used herein refers to immunoglobulin molecules and immunologically active portions of immunoglobulin molecules, i.e., molecules that contain an antigen binding site which specifically binds (immunoreacts with) an antigen, such as CCP. Examples of immunologically active portions of immunoglobulin molecules include F(ab) and F(ab′)₂ fragments which can be generated by treating the antibody with an enzyme such as pepsin. The invention provides polyclonal and monoclonal antibodies that bind CCP. The term “monoclonal antibody” or “monoclonal antibody composition”, as used herein, refers to a population of antibody molecules that contain only one species of an antigen binding site capable of immunoreacting with a particular epitope of CCP. A monoclonal antibody composition thus typically displays a single binding affinity for a particular CCP protein with which it immunoreacts.

Polyclonal anti-CCP antibodies can be prepared as described above by immunizing a suitable subject with a CCP immunogen. The anti-CCP antibody titer in the immunized subject can be monitored over time by standard techniques, such as with an enzyme linked immunosorbent assay (ELISA) using immobilized CCP. If desired, the antibody molecules directed against CCP can be isolated from the mammal (e.g., from the blood) and further purified by well known techniques, such as protein A chromatography to obtain the IgG fraction. At an appropriate time after immunization, e.g., when the anti-CCP antibody titers are highest, antibody-producing cells can be obtained from the subject and used to prepare monoclonal antibodies by standard techniques, such as the hybridoma technique originally described by Kohler and Milstein (1975) Nature 256:495-497) (see also, Brown et al. (1981) J Immunol 127:539-46; Brown et al. (1980) J. Biol. Chem. 0.255:4980-83; Yeh et al. (1976) Proc. Natl. Acad. Sci. USA 76:2927-31; and Yeh et al. (1982) Int. J. Cancer 29:269-75), the more recent human B cell hybridoma technique (Kozbor et al. (1983) Immunol Today 4:72), the EBV-hybridoma technique (Cole et al. (1985), Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, Inc., pp. 77-96) or trioma techniques. The technology for producing monoclonal antibody hybridomas is well known (see generally R. H. Kenneth, in Monoclonal Antibodies: A New Dimension In Biological Analyses, Plenum Publishing Corp., New York, N.Y. (1980); E. A. Lerner (1981) Yale J. Biol. Med., 54:387-402; M. L. Gefter et al. (1977) Somatic Cell Genet. 3:231-36). Briefly, an immortal cell line (typically a myeloma) is fused to lymphocytes (typically splenocytes) from a mammal immunized with a CCP immunogen as described above, and the culture supernatants of the resulting hybridoma cells are screened to identify a hybridoma producing a monoclonal antibody that binds CCP.

Any of the many well known protocols used for fusing lymphocytes and immortalized cell lines can be applied for the purpose of generating an anti-CCP monoclonal antibody (see, e.g., G. Galfre et al. (1977) Nature 266:55052; Gefter et al. Somatic Cell Genet., cited supra; Lerner, Yale J. Biol. Med., cited supra; Kenneth, Monoclonal Antibodies, cited supra). Moreover, the ordinarily skilled worker will appreciate that there are many variations of such methods which also would be useful. Typically, the immortal cell line (e.g., a myeloma cell line) is derived from the same mammalian species as the lymphocytes. For example, murine hybridomas can be made by fusing lymphocytes from a mouse immunized with an immunogenic preparation of the present invention with an immortalized mouse cell line. Preferred immortal cell lines are mouse myeloma cell lines that are sensitive to culture medium containing hypoxanthine, aminopterin and thymidine (“HAT medium”). Any of a number of myeloma cell lines can be used as a fusion partner according to standard techniques, e.g., the P3-NS1/1-Ag4-1, P3-x63-Ag8.653 or Sp2/O-Ag14 myeloma lines. These myeloma lines are available from ATCC. Typically, HAT-sensitive mouse myeloma cells are fused to mouse splenocytes using polyethylene glycol (“PEG”). Hybridoma cells resulting from the fusion are then selected using HAT medium, which kills unfused and unproductively fused myeloma cells (unfused splenocytes die after several days because they are not transformed). Hybridoma cells producing a monoclonal antibody of the invention are detected by screening the hybridoma culture supernatants for antibodies that bind CCP, e.g., using a standard ELISA assay.

Alternative to preparing monoclonal antibody-secreting hybridomas, a monoclonal anti-CCP antibody can be identified and isolated by screening a recombinant combinatorial immunoglobulin library (e.g., an antibody phage display library) with CCP to thereby isolate immunoglobulin library members that bind CCP. Kits for generating and screening phage display libraries are commercially available (e.g., the Pharmacia Recombinant Phage Antibody System, Catalog No. 27-9400-01; and the Stratagene SurfZAP™ Phage Display Kit, Catalog No. 240612). Additionally, examples of methods and reagents particularly amenable for use in generating and screening antibody display library can be found in, for example, Ladner et al. U.S. Pat. No. 5,223,409; Rang et al. PCT International Publication No. WO 92/18619; Dower et al. PCT International Publication No. WO 91/17271; Winter et al. PCT International Publication WO 92/20791; Markland et al. PCT International Publication No. WO 92/15679; Breitling et al. PCT International Publication WO 93/01288; McCafferty et al. PCT International Publication No. WO 92/01047; Garrard et al. PCT International Publication No. WO 92/09690; Ladner et al. PCT International Publication No. WO 90/02809; Fuchs et al. (1991) Bio/Technology 9:13704372; Hay et al. (1992) Hum. Antibod. Hybridomas 3:81-85; Huse et al. (1989) Science 246:1275-1281; Griffiths et al. (1993) EMBO J 12:725-734; Hawkins et al. (1992) J. Mol. Biol. 226:889-896; Clarkson et al. (1991) Nature 352:624-628; Gram et al. (1992) Proc. Natl. Acad. Sci. USA 89:3576-3580; Garrad et al. (1991) Bio/Technology 9:1373-1377; Hoogenboom et al. (1991) Nuc. Acid Res. 19:4133-4137; Barbas et al. (1991) Proc. Natl. Acad. Sci. USA 88:7978-7982; and McCafferty et al. Nature (1990) 348:552-554.

Additionally, recombinant anti-CCP antibodies, such as chimeric and humanized monoclonal antibodies, comprising both human and non-human portions, which can be made using standard recombinant DNA techniques, are within the scope of the invention. Such chimeric and humanized monoclonal antibodies can be produced by recombinant DNA techniques known in the art, for example using methods described in Robinson et al. International Application No. PCT/US86/02269; Akira, et al. European Patent Application 184,187; Taniguchi, M., European Patent Application 171,496; Morrison et al. European Patent Application 173,494; Neuberger et al. PCT International Publication No. WO 86/01533; Cabilly et al. U.S. Pat. No. 4,816,567; Cabilly et al. European Patent Application 125,023; Better et al. (1988) Science 240:1041-1043; Liu et al. (1987) Proc. Natl. Acad. Sci. USA 84:3439-3443; Liu et al. (1987) J. Immunol. 139:3521-3526; Sun et al. (1987) Proc. Natl. Acad. Sci. USA 84:214-218; Nishimura et al. (1987) Canc. Res. 47:999-1005; Wood et al. (1985) Nature 314:446-449; and Shaw et al, (1988) J. Natl. Cancer Inst. 80:1553-1559); Morrison, S. L. (1985) Science 229:1202-1207; Oi et al. (1986) BioTechniques 4:214; Winter U.S. Pat. No. 5,225,539; Jones et al. (1986) Nature 321:552-525; Verhoeyan et al. (1988) Science 239:1534; and Beidler et al. (1988) J. Immunol. 141:4053-4060.

An anti-CCP antibody (e.g., monoclonal antibody) can be used to isolate CCP by standard techniques, such as affinity chromatography or immunoprecipitation. An anti-CCP antibody can facilitate the purification of natural CCP from cells and of recombinantly produced CCP expressed in host cells. Moreover, an anti-CCP antibody can be used to detect CCP protein (e.g., in a cellular lysate or cell supernatant) in order to evaluate the abundance and pattern of expression of the CCP protein. These antibodies can also be used, for example, for the immunoprecipitation and immunolocalization of proteins according to the invention as well as for the monitoring of the synthesis of such proteins, for example, in recombinant organisms, and for the identification of compounds interacting with the protein according to the invention.

Anti-CCP antibodies can be used diagnostically to monitor protein levels in tissue as part of a clinical testing procedure, e.g., to, for example, determine the efficacy of a given treatment regimen. Detection can be facilitated by coupling (i.e., physically linking) the antibody to a detectable substance. Examples of detectable substances include various enzymes, prosthetic groups, fluorescent materials, luminescent materials, bioluminescent materials, and radioactive materials. Examples of suitable enzymes include horseradish peroxidase, alkaline phosphatase, -galactosidase, or acetylcholinesterase; examples of suitable prosthetic group complexes include streptavidin/biotin and avidin/biotin; examples of suitable fluorescent materials include umbelliferone, fluorescein, fluorescein isothiocyanate, rhodamine, dichlorotriazinylamine fluorescein, dansyl chloride or phycoerythrin; an example of a luminescent material includes luminol; examples of bioluminescent materials include luciferase, luciferin, and aequorin, and examples of suitable radioactive material include ¹²⁵I, ¹³¹I, ³⁵S or ³H.

III. Computer Readable Means

The CCP nucleotide sequences of the invention (e.g., SEQ ID NO:1-66 or 228-239) or amino acid sequences of the invention (e.g., SEQ ID NO:67-132, 205, 211, 215-216, or 220-227) are also provided in a variety of mediums to facilitate use thereof. As used herein, “provided” refers to a manufacture, other than an isolated nucleic acid or amino acid molecule, which contains a nucleotide or amino acid sequences of the present invention. Such a manufacture provides the nucleotide or amino acid sequences, or a subset thereof (e.g., a subset of open reading frames (ORI's)) in a form which allows a skilled artisan to examine the manufacture using means not directly applicable to examining the nucleotide or amino acid sequences, or a subset thereof, as they exist in nature or in purified form.

In one application of this embodiment, a nucleotide or amino acid sequence of the present invention can be recorded on computer readable media. As used herein “computer readable media” includes any medium that can be read and accessed directly by a computer. Such media include, but are not limited to: magnetic storage media, such as floppy discs, hard disc storage medium, and magnetic tape; optical storage media such a CD-ROM; electrical storage media such as RAM and ROM; and hybrids of these categories such as magnetic/optical storage media. The skilled artisan will readily appreciate how any of the presently known computer readable mediums can be used to create a manufacture comprising computer readable medium having recorded thereon a nucleotide or amino acid sequence of the present invention.

As used herein “recorded” refers to a process of storing information on computer readable medium. The skilled artisan can readily adopt any of the presently known methods for recording information on a computer readable medium to generate manufactures comprising the nucleotide or amino acid sequence information of the present invention.

A variety of data storage structures are available to a skilled artisan for creating a computer readable medium having recorded thereon a nucleotide or amino acid sequence of the present invention. The choice of the data storage structure will generally be based on the means chosen to access the stored information. In addition, a variety of data processor programs and formats can be used to store the nucleotide sequence information of the present invention on computer readable medium. The sequence information can be represented in a word processing text file, formatted in commercially-available software such as WordPerfect and Microsoft Word, or represented in the form of an ASCII file, stored in a database application, such as DB2, Sybase Oracle, or the like. The skilled artisan can readily adapt any number of dataprocessor structuring formats (e.g., text file or database) in order to obtain computer readable medium having recorded thereon the nucleotide sequence information of the present invention.

By providing the nucleotide or amino acid sequences of the invention in computer readable form, the skilled artisan can routinely access the sequence information for a variety of purposes. For example, one skilled in the art can use the nucleotide or amino acid sequences of the invention in computer readable form to compare a target sequence or target structural motif with the sequence information stored within the data storage means. Search means are used to identity fragments or regions of the sequences of the invention which match a particular target sequence or target motif As used herein, a “target sequence” can be any DNA or amino acid sequence of six or more nucleotide or two or more amino acids. A skilled artisan can readily recognize that the longer a target sequence is, the less likely a target sequence will be present as a random occurrence in the database. The most preferred sequence length of a target sequence is from about 10 to 100 amino acids or form about 30 to 300 nucleotide residues. However, it is well recognized that commercially important fragments, such as sequence fragments involved in gene expression and protein processing, may be shorter length.

As used herein, “a target structural motif,” or “target motif,” refers to any rationally selected sequence or combination of sequences in which the sequence(s) are chosen based on a three-dimensional configuration which is formed upon the folding of the target motif. There are a variety of target motifs known in the art. Protein target motifs include, but are not limited to, enzyme active sites and signal sequences. Nucleic acid target motifs include, but are not limited to, promoter sequences, hairpin structures and inducible expression elements (protein binding sequences).

Computer software is publicly available which allows a skilled artisan to access sequence information provided in a computer readable medium for analysis and comparison to other sequences. A variety of known algorithms are disclosed publicly and a variety of commercially available software of conducting search means are and can be used in the computer-based systems of the present invention. Examples of such software include, but are not limited to, MacPatter (EMBL), BLASTN and BASTX (NCBIA).

For example, software which implements the BLAST (Altschul et al. (1990) J. Mol. Biol. 215:403-410) and BLAZE (Brutlag et al. (1993) Comp. Chem. 17:203-207) search algorithms on a Sybase system can be used to identify open reading frames (ORFs) of the sequences of the invention which contain homology to ORFs or proteins from other libraries. Such ORFs are protein encoding fragments and are useful in producing commercially important proteins such as enzyme used in various reactions and in the production of commercially useful metabolites.

IV. Recombinant Expression Vectors and Host Cells

Another aspect of the invention pertains to vectors, preferably expression vectors, containing a nucleic acid encoding a CCP protein (or a portion thereof). As used herein, the term “vector” refers to a nucleic acid molecule capable of transporting another nucleic acid to which it has been linked. One type of vector is a “plasmid”, which refers to a circular double stranded DNA loop into which additional DNA segments can be ligated. Another type of vector is a viral vector, wherein additional DNA segments can be ligated into the viral genome. Certain vectors are capable of autonomous replication in a host cell into which they are introduced (e.g., bacterial vectors having a bacterial origin of replication and episomal mammalian vectors). Other vectors (e.g., non-episomal mammalian vectors) are integrated into the genome of a host cell upon introduction into the host cell, and thereby are replicated along with the host genome. Moreover, certain vectors are capable of directing the expression of genes to which they are operatively linked. Such vectors are referred to herein as “expression vectors”. In general, expression vectors of utility in recombinant DNA techniques are often in the form of plasmids. In the present specification, “plasmid” and “vector” can be used interchangeably as the plasmid is the most commonly used form of vector. However, the invention is intended to include such other forms of expression vectors, such as viral vectors (e.g., replication defective retroviruses, adenoviruses and adeno-associated viruses), which serve equivalent functions.

The recombinant expression vectors of the invention comprise a nucleic acid of the invention in a form suitable for expression of the nucleic acid in a host cell, e.g., a plant cell, which means that the recombinant expression vectors include one or more regulatory sequences, selected on the basis of the host cells to be used for expression, which is operatively linked to the nucleic acid sequence to be expressed. Within a recombinant expression vector, “operably linked” is intended to mean that the nucleotide sequence of interest is linked to the regulatory sequence(s) in a manner which allows for expression of the nucleotide sequence (e.g., in an in vitro transcription/translation system or in a host cell when the vector is introduced into the host cell). The term “regulatory sequence” is intended to includes promoters, enhancers and other expression control elements (e.g., polyadenylation signals). Such regulatory sequences are described, for example, in Goeddel; Gene Expression Technology: Methods in Enzymology 185, Academic Press, San Diego, Calif. (1990). Regulatory sequences include those which direct constitutive expression of a nucleotide sequence in many types of host cell and those which direct expression of the nucleotide sequence only in certain host cells (e.g., tissue-specific regulatory sequences). It will be appreciated by those skilled in the art that the design of the expression vector can depend on such factors as the choice of the host cell to be transformed, the level of expression of protein desired, and the like. The expression vectors of the invention can be introduced into host cells to thereby produce proteins or peptides, including fusion proteins or peptides, encoded by nucleic acids as described herein (e.g., CCP proteins, mutant forms of CCP proteins, fusion proteins, and the like).

The vectors of the invention comprise a selectable and/or scorable marker. Selectable marker genes useful for the selection of transformed plant cells, callus, plant tissue and plants are well known to those skilled in the art and comprise, for example, antimetabolite resistance as the basis of selection for dhfr, which confers resistance to methotrexate (Reiss, Plant Physiol. (Life Sci. Adv.) 13 (1994), 143-149); npt, which confers resistance to the aminoglycosides neomycin, kanamycin and paromycin (Herrera-Estrella, EMBO J. 2 (1983), 987-995) and hygro, which confers resistance to hygromycin (Marsh, Gene 32 (1984), 481-485). Additional selectable genes have been described, namely trpB, which allow cells to utilize indole in place of tryptophan; hisD, which allows cells to utilize histinol in place of histidine (Hartman, Proc. Natl. Acad. Sci. USA 85 (1988), 8047); mannose-6-phosphate isomerase which allows cells to utilize mannose (WO 94/20627) and ODC (ornithine decarboxylase) which confers resistance to the ornithine decarboxylase inhibitor, 2-(difluoromethyl)-DL-ornithine, DFMO (McConlogue, 1987, In: Current Communications in Molecular Biology, Cold Spring Harbor Laboratory ed.) or deaminase from Aspergillus terreus which confers resistance to Blasticidin S (Tamura, Biosci. Biotechnol. Biochem. 59 (1995), 2336-2338).

Useful scorable markers are also known to those skilled in the art and are commercially available. Advantageously, the marker is a gene encoding luciferase (Giacomin, Pl. Sci. 116 (1996), 59-72; Scikantha, J. Bact. 178 (1996), 121), green fluorescent protein (Gerdes, FEBS Lett. 389 (1996), 44-47) or B-glucuronidase (Jefferson, EMBO J. 6 (1987), 3901-3907). This embodiment is particularly useful for simple and rapid screening of cells, tissues and organisms containing a vector of the invention.

A “plant promoter” is a promoter capable of initiating transcription in plant cells. Exemplary plant promoters include, but are not limited to, those that are obtained from plants, plant viruses, and bacteria. Preferred promoters may contain additional copies of one or more specific regulatory elements, to further enhance expression and/or to alter the spatial expression and/or temporal expression of a nucleic acid molecule to which it is operably connected. For example, copper-responsive, glucocorticoid-responsive or dexamethasone-responsive regulatory elements may be placed adjacent to a heterologous promoter sequence driving expression of a nucleic acid molecule to confer copper inducible, glucocorticoid-inducible, or dexamethasone-inducible expression respectively, on said nucleic acid molecule. Examples of promoters under developmental control include promoters that preferentially initiate transcription in certain tissues, such as leaves, roots, seeds, endosperm, embryos, fibers, xylem vessels, tracheids, or sclerenchyma. Such promoters are referred to as “tissue preferred.” Promoters which initiate transcription only in certain tissue are referred to as “tissue specific.” A “cell type” specific promoter primarily drives expression in certain cell types in one or more organs, for example, vascular cells in roots or leaves. An “inducible” promoter is a promoter which is under environmental control. Examples of environmental conditions that may effect transcription by inducible promoters include anaerobic conditions or the presence of light. Tissue specific, tissue preferred, cell type specific, and inducible promoters constitute the class of “non-constitutive” promoters. A “constitutive” promoter is a promoter which is active under most environmental conditions.

Another aspect of the invention pertains to host cells into which a recombinant expression vector of the invention has been introduced. The terms “host cell” and “recombinant host cell” are used interchangeably herein. It is understood that such terms refer not only to the particular subject cell but to the progeny or potential progeny of such a cell. Because certain modifications may occur in succeeding generations due to either mutation or environmental influences, such progeny may not, in fact, be identical to the parent cell, but are still included within the scope of the term as used herein.

A host cell can be any prokaryotic or eukaryotic cell. For example, a CCP protein can be expressed in plant cells, bacterial cells such as E. coli, insect cells, yeast or mammalian cells (such as Chinese hamster ovary cells (CHO) or COS cells). Other suitable host cells are known to those skilled in the art.

Vector DNA can be introduced into prokaryotic or eukaryotic cells via conventional transformation or transfection techniques. As used herein, the terms “transformation” and “transfection” are intended to refer to a variety of art-recognized techniques for introducing foreign nucleic acid (e.g., DNA) into a host cell, including calcium phosphate or calcium chloride co-precipitation, DEAE-dextran-mediated transfection, lipofection, or electroporation. Suitable methods for transforming or transfecting host cells can be found in Sambrook, et al. (Molecular Cloning: A Laboratory Manual. 2nd, ed., Cold Spring Harbor Laboratory, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1989), and other laboratory manuals.

Means for introducing a recombinant expression vector of this invention into plant tissue or cells include, but are not limited to; transformation using CaCl₂ and variations thereof, in particular the method described by Hanahan (J. Mol. Biol. 166, 557-560, 1983), direct DNA uptake into protoplasts (Krens et al, Nature 296: 72-74, 1982; Paszkowski et al, EMBO J. 3:2717-2722, 1984), PEG-mediated uptake to protoplasts (Armstrong et al, Plant Cell Reports 9: 335-339, 1990) microparticle bombardment, electroporation (Fromm et al., Proc. Natl. Acad. Sci. (USA) 82:5824-5828, 1985), microinjection of DNA (Crossway et al., Mol. Gen. Genet. 202:179-185, 1986), microparticle bombardment of tissue explants or cells (Christou et al, Plant Physiol 87: 671-674, 1988; Sanford, Particulate Science and Technology 5: 27-37, 1987), vacuum-infiltration of tissue with nucleic acid, or in the case of plants, T-DNA-mediated transfer from Agrobacterium to the plant tissue as described essentially by An et al. (EMBO J. 4:277-284, 1985), Herrera-Estrella et al. (Nature 303: 209-213, 1983a; EMBO J. 2: 987-995, 1983b; In: Plant Genetic Engineering, Cambridge University Press, N.Y., pp 63-93, 1985), or in planta method using Agrobacterium tumefaciens such as that described by Bechtold et al., (C. R. Acad. Sci. (Paris, Sciences de la vie/Life Sciences)316: 1194-1199, 1993), Clough et al (Plant J. 16: 735-743, 1998), Trieu et al. (Plant J. 22:531-541, 2000) or Kloti (WO01/12828, 2001). Methods for transformation of monocotyledonous plants are well known in the art and include Agrobacterium-mediated transformation (Cheng et al. (1997) WO 97/48814; Hansen (1998) WO 98/54961; Hiei et al. (1994) WO 94/00977; Hiei et al. (1998) WO 98/17813; Rikiishi et al. (1999) WO 99/04618; Saito et al. (1995) WO 95/06722), microprojectile bombardment (Adams et al. (1999) U.S. Pat. No. 5,969,213; Bowen et al. (1998) U.S. Pat. No. 5,736,369; Chang et al. (1994) WO 94/13822; Lundquist et al. (1999) U.S. Pat. No. 5,874,265/U.S. Pat. No. 5,990,390; Vasil and Vasil (1995) U.S. Pat. No. 5,405,765; Walker et al. (1999) U.S. Pat. No. 5,955,362), DNA uptake (Eval et al. (1993) WO 93/181,168), microinjection of Agrobacterium cells (von Holt 1994 DE 4309203), sonication (Finer et al. (1997) U.S. Pat. No. 5,693,512) and flower-dip or in planta-transformation (Kloti, WO01/12828, 2001).

The vector DNA may further comprise a selectable marker gene to facilitate the identification and/or selection of cells which are transfected or transformed with a genetic construct. Suitable selectable marker genes contemplated herein include the ampicillin resistance (Amp^(r)), tetracycline resistance gene Tc^(r)), bacterial kanamycin resistance gene (Kang, phosphinothricin resistance gene, neomycin phosphotransferase gene (nptII), hygromycin resistance gene, β-glucuronidase (GUS) gene, chloramphenicol acetyltransferase (CAT) gene, green fluorescent protein (gfp) gene (Haseloff et al, 1997), and luciferase gene.

For microparticle bombardment of cells, a microparticle is propelled into a cell to produce a transformed cell. Any suitable ballistic cell transformation methodology and apparatus can be used in performing the present invention. Exemplary apparatus and procedures are disclosed by Stomp et al. (U.S. Pat. No. 5,122,466) and Sanford and Wolf (U.S. Pat. No. 4,945,050). When using ballistic transformation procedures, the gene construct may incorporate a plasmid capable of replicating in the cell to be transformed. Examples of microparticles suitable for use in such systems include 1 to 5 μm gold spheres. The DNA construct may be deposited on the microparticle by any suitable technique, such as by precipitation.

A whole plant may be regenerated from the transformed or transfected cell, in accordance with procedures well known in the art. Plant tissue capable of subsequent clonal propagation, whether by organogenesis or embryogenesis, may be transformed with a gene construct of the present invention and a whole plant regenerated therefrom. The particular tissue chosen will vary depending on the clonal propagation systems available for, and best suited to, the particular species being transformed. Exemplary tissue targets include leaf disks, pollen, embryos, cotyledons, hypocotyls, megagametophytes, callus tissue, existing meristematic tissue (e.g., apical meristem, axillary buds, and root meristems), and induced meristem tissue (e.g., cotyledon meristem and hypocotyl meristem).

The term “organogenesis”, as used herein, includes a process by which shoots and roots are developed sequentially from meristematic centres.

The term “embryogenesis”, as used herein, includes a process by which shoots and roots develop together in a concerted fashion (not sequentially), whether from somatic cells or gametes.

Preferably, the plant is produced according to the methods of the invention by transfecting or transforming the plant with a genetic sequence, or by introducing to the plant a protein, by any art-recognized means, such as microprojectile bombardment, microinjection, Agrobacterium-mediated transformation (including in planta transformation), protoplast fusion, or electroporation, amongst others. Most preferably the plant is produced by Agrobacterium-mediated transformation. Agrobacterium-mediated transformation or agrolistic transformation of plants, yeast, moulds or filamentous fungi is based on the transfer of part of the transformation vector sequences, called the T-DNA, to the nucleus and on integration of said T-DNA in the genome of said eukaryote.

The term “Agrobacterium” as used herein, includes a member of the Agrobacteriaceae, more preferably Agrobacterium or Rhizobacterium and most preferably Agrobacterium tumefaciens.

The term “T-DNA”, or “transferred DNA”, as used herien, includes the transformation vector flanked by T-DNA borders which is, after activation of the Agrobacterium vir genes, nicked at the T-DNA borders and is transferred as a single stranded DNA to the nucleus of an eukaryotic cell.

As used herein, the terms “T-DNA borders”, “T-DNA border region”, or “border region” include either right T-DNA borders (RB) or left T-DNA borders (LB), which comprise a core sequence flanked by a border inner region as part of the T-DNA flanking the border and/or a border outer region as part of the vector backbone flanking the border. The core sequences comprise 22 bp in case of octopine-type vectors and 25 bp in case of nopaline-type vectors. The core sequences in the right border region and left border region form imperfect repeats.

As used herein, the term “T-DNA transformation vector” or “T-DNA vector” includes any vector encompassing a T-DNA sequence flanked by a right and left T-DNA border consisting of at least the right and left border core sequences, respectively, and used for transformation of any eukaryotic cell.

As used herein, the term “T-DNA vector backbone sequence” or “T-DNA vector backbone sequences” includes all DNA of a T-DNA containing vector that lies outside of the T-DNA borders and, more specifically, outside the nicking sites of the border core imperfect repeats.

The present invention includes optimized T-DNA vectors such that vector backbone integration in the genome of a eukaryotic cell is minimized or absent. The term “optimized T-DNA vector” as used herein includes a T-DNA vector designed either to decrease or abolish transfer of vector backbone sequences to the genome of a eukaryotic cell. Such T-DNA vectors are known to the one of skill in the art and include those described by Hanson et al. (1999) and by Stuiver et al. (1999—WO9901563).

The current invention clearly considers the inclusion of a DNA sequence encoding a CCP, homologue, analogue, derivative or immunologically active fragment thereof as defined supra, in any T-DNA vector comprising binary transformation vectors, super-binary transformation vectors, co-integrate transformation vectors, R1-derived transformation vectors as well as in T-DNA carrying vectors used in agrolistic transformation.

As used herein, the term “binary transformation vector” includes a T-DNA transformation vector comprising: a T-DNA region comprising at least one gene of interest and/or at least one selectable marker active in the eukaryotic cell to be transformed; and a vector backbone region comprising at least origins of replication active in E. coli and Agrobacterium and markers for selection in E. coli and Agrobacterium. Alternatively, replication of the binary transformation vector in Agrobacterium is dependent on the presence of a separate helper plasmid. The binary vector pGreen and the helper plasmid pSoup form an example of such a system (Hellens et al. (2000), Plant Mol. Biol. 42, 819-832; http://www.pgreen.ac.uk).

The T-DNA borders of a binary transformation vector can be derived from octopine-type or nopaline-type Ti plasmids or from both. The T-DNA of a binary vector is only transferred to a eukaryotic cell in conjunction with a helper plasmid. As used herein, the term “helper plasmid” includes a plasmid that is stably maintained in Agrobacterium and is at least carrying the set of vir genes necessary for enabling transfer of the T-DNA. The set of vir genes can be derived from either octopine-type or nopaline-type Ti plasmids or from both.

As used herein, the term “super-binary transformation vector” includes a binary transformation vector additionally carrying in the vector backbone region a vir region of the Ti plasmid pTiBo542 of the super-virulent A. tumefaciens strain A281 (EP0604662, EP0687730). Super-binary transformation vectors are used in conjunction with a helper plasmid.

As used herein, the term “co-integrate transformation vector” includes a T-DNA vector at least comprising: a T-DNA region comprising at least one gene of interest and/or at least one selectable marker active in plants; and a vector backbone region comprising at least origins of replication active in Escherichia coli and Agrobacterium, and markers for selection in E. coli and Agrobacterium, and a set of vir genes necessary for enabling transfer of the T-DNA. The T-DNA borders and the set of vir genes of the T-DNA vector can be derived from either octopine-type or nopaline-type Ti plasmids or from both.

The term “Ri-derived plant transformation vector” includes a binary transformation vector in which the T-DNA borders are derived from a Ti plasmid and the binary transformation vector being used in conjunction with a ‘helper’ Ri-plasmid carrying the necessary set of vir genes.

The terms “agrolistics”, “agrolistic transformation” or “agrolistic transfer” include a transformation method combining features of Agrobacterium-mediated transformation and of biolistic DNA delivery. As such, a T-DNA containing target plasmid is co-delivered with DNA/RNA enabling in planta production of VirD1 and VirD2 with or without VirE2 (Hansen and Chilton 1996; Hansen et al. 1997; Hansen and Chilton 1997—WO9712046).

A host cell of the invention, such as a prokaryotic or eukaryotic host cell in culture, can be used to produce (i.e., express) a CCP protein. Accordingly, the invention further provides methods for producing a CCP protein using the host cells of the invention. In one embodiment, the method comprises culturing the host cell of invention (into which a recombinant expression vector encoding a CCP protein has been introduced) in a suitable medium such that a CCP protein is produced. In another embodiment, the method further comprises isolating a CCP protein from the medium or the host cell.

The host cells of the invention can also be used to produce transgenic plant or non-human transgenic animals in which exogenous CCP sequences have been introduced into their genome or homologous recombinant plants or animals in which endogenous CCP sequences have been altered. Such plants and animals are useful for studying the function and/or activity of a CCP and for identifying and/or evaluating modulators of CCP activity.

Trangenic Plants

As used herein, “transgenic plant” includes a plant which comprises within its genome a heterologous polynucleotide. Generally, the heterologous polynucleotide is stably integrated within the genome such that the polynucleotide is passed on to successive generations. The heteroglogous polynucleotide may be integrated into the genome alone or as part of a recombinant expression cassette. “Transgenic” is used herein to include any cell, cell line, callus, tissue, plant part or plant, the genotype of which has been altered by the presence of heterologous nucleic acid including those transgenics initially so altered as well as those created by sexual crosses as asexual propagation from the initial transgenic. The term “transgenic” as used herein does not encompass the alteration of the genome (chromosomal or extra-chromosomal) by conventional plant breeding methods or by naturally occurring event such as random cross-fertilization, non-recombinant viral infection, non-recombinant bacterial transformation, non-recombinant transposition, or spontaneous mutation.

A transgenic plant of the invention can be created by introducing a CCP-encoding nucleic acid into the plant by placing it under the control of regulatory elements which ensure the expression in plant cells. These regulatory elements may be heterologous or homologous with respect to the nucleic acid molecule to be expressed as well with respect to the plant species to be transformed. In general, such regulatory elements comprise a promoter active in plant cells. These promoters can be used to modulate (e.g. increase or decrease) CCP content and/or composition in a desired tissue. To obtain expression in all tissues of a transgenic plant, preferably constitutive promoters are used, such as the 35 S promoter of CaMV (Odell, Nature 313 (1985), 810-812) or promoters from such genes as rice actin (McElroy et al. (1990) Plant Cell 2:163-171) maize H3 histone (Lepetit et al. (1992) Mol. Gen. Genet. 231:276-285) or promoters of the polyubiquitin genes of maize (Christensen, Plant Mol. Biol. 18 (1982), 675-689). In order to achieve expression in specific tissues of a transgenic plant it is possible to use tissue specific promoters (see, e.g., Stockhaus, EMBO J. 8 (1989), 2245-2251 or Table II, below).

TABLE II EXPRESSION GENE SOURCE PATTERN REFERENCE α-amylase (Amy32b) aleurone Lanahan, M. B., e t al., Plant Cell 4: 203- 211, 1992; Skriver, K., et al. Proc. Natl. Acad. Sci. (USA) 88: 7266-7270, 1991 cathepsin β-like gene aleurone Cejudo, F. J., et al. Plant Molecular Biology 20: 849-856, 1992. Agrobacterium rhizogenes rolB cambium Nilsson et al., Physiol. Plant. 100: 456-462, 1997 PRP genes cell wall http://salus.medium.edu/mmg/tierney/html barley Itr1 promoter endosperm synthetic promoter endosperm Vicente-Carbajosa et al., Plant J. 13: 629- 640, 1998. AtPRP4 flowers http://salus.medium.edu/mmg/tierney/html chalene synthase (chsA) flowers Van der Meer, et al., Plant Mol. Biol. 15, 95-109, 1990. LAT52 anther Twell et al Mol. Gen Genet. 217: 240-245 (1989) apetala-3 flowers chitinase fruit (berries, grapes, etc) Thomas et al. CSIRO Plant Industry, Urrbrae, South Australia, Australia; http://winetitles.com.au/gwrdc/csh95-1.html rbcs-3A green tissue (eg leaf) Lam, E. et al., The Plant Cell 2: 857-866, 1990.; Tucker et al., Plant Physiol. 113: 1303-1308, 1992. leaf-specific genes leaf Baszczynski, et al., Nucl. Acid Res. 16: 4732, 1988. AtPRP4 leaf http://salus.medium.edu/mmg/tierney/html Pinus cab-6 leaf Yamamoto et al., Plant Cell Physiol. 35: 773-778, 1994. SAM22 senescent leaf Crowell, et al., Plant Mol. Biol. 18: 459- 466, 1992. R. japonicum nif gene nodule U.S. Pat. No. 4,803,165 B. japonicum nifH gene nodule U.S. Pat. No. 5,008,194 GmENOD40 nodule Yang, et al., The Plant J. 3: 573-585. PEP carboxylase (PEPC) nodule Pathirana, et al., Plant Mol. Biol. 20: 437- 450, 1992. leghaemoglobin (Lb) nodule Gordon, et al., J. Exp. Bot. 44: 1453-1465, 1993. Tungro bacilliform virus gene phloem Bhattacharyya-Pakrasi, et al, The Plant J. 4: 71-79, 1992. sucrose-binding protein gene plasma membrane Grimes, et al., The Plant Cell 4: 1561- 1574, 1992. pollen-specific genes pollen; microspore Albani, et al., Plant Mol. Biol. 15: 605, 1990; Albani, et al., Plant Mol. Biol. 16: 501, 1991) Zm13 pollen Guerrero et al Mol. Gen. Genet. 224: 161- 168 (1993) apg gene microspore Twell et al Sex. Plant Reprod. 6: 217-224 (1993) maize pollen-specific gene pollen Hamilton, et al., Plant Mol. Biol. 18: 211- 218, 1992. sunflower pollen-expressed gene pollen Baltz, et al., The Plant J. 2: 713-721, 1992. B. napus pollen-specific gene pollen; anther; tapetum Arnoldo, et al., J. Cell. Biochem., Abstract No. Y101, 204, 1992. root-expressible genes roots Tingey, et al., EMBO J. 6: 1, 1987. tobacco auxin-inducible gene root tip Van der Zaal, et al., Plant Mol. Biol. 16, 983, 1991. β-tubulin root Oppenheimer, et al., Gene 63: 87, 1988. tobacco root-specific genes root Conkling, et al., Plant Physiol. 93: 1203, 1990. B. napus G1-3b gene root U.S. Pat. No. 5,401,836 SbPRP1 roots Suzuki et al., Plant Mol. Biol. 21: 109- 119, 1993. AtPRP1; AtPRP3 roots; root hairs http://salus.medium.edu/mmg/tierney/html RD2 gene root cortex http://www2.cnsu.edu/ncsu/research TobRB7 gene root vasculature http://www2.cnsu.edu/ncsu/research AtPRP4 leaves; flowers; lateral http://salus.medium.edu/mmg/tierney/html root primordia seed-specific genes seed Simon, et al., Plant Mol. Biol. 5: 191, 1985; Scofield, et al., J. Biol. Chem. 262: 12202, 1987.; Baszczynski, et al., Plant Mol. Biol. 14: 633, 1990. Brazil Nut albumin seed Pearson, et al., Plant Mol. Biol. 18: 235- 245, 1992. legumin seed Ellis, et al., Plant Mol. Biol. 10: 203-214, 1988. glutelin (rice) seed Takaiwa, et al., Mol. Gen. Genet. 208: 15-22, 1986; Takaiwa, et al., FEBS Letts. 221: 43-47, 1987. zein seed Matzke et al Plant Mol Biol, 14(3): 323- 32 1990 napA seed Stalberg, et al, Planta 199: 515-519, 1996. sunflower oleosin seed (embryo and dry Cummins, et al., Plant Mol. Biol. 19: seed) 873-876, 1992 LEAFY shoot meristem Weigel et al., Cell 69: 843-859, 1992. Arabidopsis thaliana knat1 shoot meristem Accession number AJ131822 Malus domestica kn1 shoot meristem Accession number Z71981 CLAVATA1 shoot meristem Accession number AF049870 stigma-specific genes stigma Nasrallah, et al., Proc. Natl. Acad. Sci. USA 85: 5551, 1988; Trick, et al., Plant Mol. Biol. 15: 203, 1990. class I patatin gene tuber Liu et al., Plant Mol. Biol. 153: 386-395, 1991. blz2 endosperm EP99106056.7 PCNA rice meristem Kosugi et al, Nucleic Acids Research 19: 1571-1576, 1991; Kosugi S. and Ohashi Y, Plant Cell 9: 1607-1619, 1997. The promoters listed in the foregoing table are provided for the purposes of exemplification only and the present invention is not to be limited by the list provided therein. Those skilled in the art will readily be in a position to provide additional promoters that are useful in performing the present invention. The promoters listed may also be modified to provide specificity of expression as required.

Known are also promoters which are specifically active in tubers of potatoes or in seeds of different plants species, such as maize, Vicia, wheat, barley and the like. Inducible promoters may be used in order to be able to exactly control expression under certain environmental or developmental conditions such as pathogens, anaerobia, or light. Examples of inducible promoters include the promoters of genes encoding heat shock proteins or microspore-specific regulatory elements (WO96/16182). Furthermore, the chemically inducible Tet-system may be employed (Gatz, Mol. Gen. Genet. 227 (1991); 229-237). Further suitable promoters are known to the person skilled in the art and are described, e.g., in Ward (Plant Mol. Biol. 22 (1993), 361-366). The regulatory elements may further comprise transcriptional and/or translational enhancers functional in plants cells. Furthermore, the regulatory elements may include transcription termination signals, such as a poly-A signal, which lead to the addition of a poly A tail to the transcript which may improve its stability.

In the case that a nucleic acid molecule according to the invention is expressed in the sense orientation, the coding sequence can be modified such that the protein is located in any desired compartment of the plant cell, e.g., the nucleus, endoplasmatic reticulum, the vacuole, the mitochondria, the plastids, the apoplast, or the cytoplasm.

Methods for the introduction of foreign DNA into plants are also well known in the art. These include, for example, the transformation of plant cells or tissues with T-DNA using Agrobacterium tumefaciens or Agrobacterium rhizogenes, the fusion of protoplasts, direct gene transfer (see, e.g., EP-A 164 575), injection, electroporation, biolistic methods like particle bombardment, pollen-mediated transformation, plant RNA virus-mediated transformation, liposome-mediated transformation, transformation using wounded or enzyme-degraded immature embryos, or wounded or enzyme-degraded embryogenic callus and other methods known in the art. The vectors used in the method of the invention may contain further functional elements, for example “left border”- and “right border”-sequences of the T-DNA of Agrobacterium which allow for stably integration into the plant genome. Furthermore, methods and vectors are known to the person skilled in the art which permit the generation of marker free transgenic plants, i.e., the selectable or scorable marker gene is lost at a certain stage of plant development or plant breeding. This can be achieved by, for example, cotransformation (Lyznik, Plant Mol. Biol. 13 (1989), 151-161; Peng, Plant Mol. Biol. 27 (1995), 91-104) and/or by using systems which utilize enzymes capable of promoting homologous recombination in plants (see, e.g., WO97/08331; Bayley, Plant Mol. Biol. 18 (1992), 353-361); Lloyd, Mol. Gen. Genet. 242 (1994), 653-657; Maeser, Mol. Gen. Genet. 230 (1991), 170-176; Onouchi, Nucl. Acids Res. 19 (1991), 6373-6378). Methods for the preparation of appropriate vectors are described by, e.g., Sambrook (Molecular Cloning; A Laboratory Manual, 2nd Edition (1989), Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.).

Suitable strains of Agrobacterium tumefaciens and vectors, as well as transformation of Agrobacteria, and appropriate growth and selection media are described in, for example, GV3101 (pMK90RK), Koncz, Mol. Gen. Genet. 204 (1986), 383-396; C58C1 (pGV 3850kan), Deblaere, Nucl. Acid Res. 13 (1985), 4777; Bevan, Nucleic. Acid Res. 12 (1984), 8711; Koncz, Proc. Natl. Acad. Sci. USA 86 (1989), 8467-8471; Koncz, Plant Mol. Biol. 20 (1992), 963-976; Koncz, Specialized vectors for gene tagging and expression studies. In: Plant Molecular Biology Manual Vol 2, Gelvin and Schilperoort (Eds.), Dordrecht, The Netherlands: Kluwer Academic Publ. (1994), 1-22; EP-A-120 516; Hoekema: The Binary Plant Vector System, Offsetdrukkerij Kanters B. V., Alblasserdam (1985), Chapter V, Fraley, Crit. Rev. Plant. Sci., 4, 1-46; An, EMBO J. 4 (1985), 277-287). Although the use of Agrobacterium tumefaciens is preferred in the method of the invention, other Agrobacterium strains, such as Agrobacterium rhizogenes, may be used, for example, if a phenotype conferred by said strain is desired.

Methods for the transformation using biolistic methods are known to the person skilled in the art; see, e.g., Wan, Plant Physiol. 104 (1994), 37-48; Vasil, Bio/Technology 11 (1993), 1553-1558 and Christou (1996) Trends in Plant Science 1, 423-431. Microinjection can be performed as described in Potrykus and Spangenberg (eds.), Gene Transfer To Plants. Springer Verlag, Berlin, N.Y. (1995).

The transformation of most dicotyledonous plants may be performed using the methods described above or using transformation via biolistic methods as, e.g., described above as well as protoplast transformation, electroporation of partially permeabilized cells, or introduction of DNA using glass fibers.

In general, the plants which are modified according to the invention may be derived from any desired plant species. They can be monocotyledonous plants or dicotyledonous plants, preferably they belong to plant species of interest in agriculture, wood culture or horticulture interest, such as crop plants (e.g., maize, rice, barley, wheat, rye, oats), potatoes, oil producing plants (e.g., oilseed rape, sunflower, pea nut, soy bean), cotton, sugar beet, sugar cane, leguminous plants (e.g., beans, peas), or wood producing plants, preferably trees.

The present invention also relates to a transgenic plant cell which contains (preferably stably integrated into its genome) a nucleic acid molecule of the present invention linked to regulatory elements which allow expression of the nucleic acid molecule in plant cells. The presence and expression of the nucleic acid molecule in the transgenic plant cells leads to the synthesis of a CCP protein and may lead to physiological and phenotypic changes in plants containing such cells.

Transformed plant cells which are derived by any of the above transformation techniques can be cultured to regenerate a whole plant which possesses the transformed genotype. Such regeneration techniques often rely on manipulation of certain phytohormones in a tissue culture growth medium, typically relying on a biocide and/or herbicide marker which has been introduced with a polynucleotide of the present invention.

Plant cells transformed with a plant expression vector can be regenerated, e.g., from single cells, callus tissue or leaf discs according to standard plant tissue culture techniques. It is well known in the art that various cells, tissues, and organs from almost any plant can be successfully cultured to regenerate an entire plant. Plant regeneration from cultured protoplasts is described in Evans et al., Protoplasts Isolation and Culture, Handbook of Plant Cell Culture, Macmillilan Publishing Company, New York, pp. 124-176 (1983); and Binding, Regeneration of Plants, Plant Protoplasts, CRC Press, Boca Raton, pp. 21-73 (1985).

Transformed plant cells, calli or explant can be cultured on regeneration medium in the dark for several weeks, generally about 1 to 3 weeks to allow the somatic embryos to mature. Preferred regeneration media include media containing MS salts, such as PHI-E and PHI-F media. The plant cells, calli or explant are then typically cultured on rooting medium in a light/dark cycle until shoots and roots develop. Methods for plant regeneration are known in the art and preferred methods are provided by Kamo et al., (Bot. Gaz. 146(3):324-334, 1985), West et al., (The Plant Cell 5:1361-1369. 1993), and Duncan et al. (Planta 165:322-332, 1985).

Small plantlets can then be transferred to tubes containing rooting medium and allowed to grow and develop more roots for approximately another week. The plants can then be transplanted to soil mixture in pots in the greenhouse.

The regeneration of plants containing the foreign gene introduced by Agrobacterium from leaft explants can be achieved as described by Horsch et al., Science, 227:1229-1231 (1985). In this procedure, transformants are grown in the presence of a selection agent and in a medium that induces the regeneration of shoots in the plant species being transformed as described by Fraley et al., Proc. Natl. Acad. Sci, U.S.A. 80:4803 (1983). This procedure typically produces shoots within two to four weeks and these transformant shoots are then transferred to an appropriate root-inducing medium containing the selective agent and an antibiotic to prevent bacterial growth. Transgenic plants of the present invention may be fertile or sterile.

Regeneration can also be obtained from plant callus, explants, organs, or parts thereof. Such regeneration techniques are described generally in Klee et al., Ann. Rev. of Plant Phys., 38:467-486 (1987). The regeneration of plants from either single plant protoplasts or various explants is well known in the art. See, from example, Methods for Plant Molecular Biology, A. Weissbach and H. Weissback, eds., Academic Press, Inc., San Diego, Calif. (1988). This regeneration and growth process includes the steps of selection of transformant cells and shoots, rooting ht transformant shoots and growth of the plantlets in soil. For maize cell culture and regeneration see generally, The Maize Handbook, Freeling and Walbot, Eds., Springer, New York (1994); Corn and Corn Improvement, 3^(rd) edition, Sprague and Dudley Eds., American Society of Agronomy, Madison, Wis. (1988).

One of skill will recognize that after the recombinant expression cassette is stably incorporated in transgenic plants and confirmed to be operable, it can be introduced into other plants by sexual crossing. Any of a number of standard breeding techniques can be used, depending upon the species to be crossed.

In vegetatively propagated crops, mature transgenic plants can be propagated by the taking of cuttings or by tissue culture techniques to produce multiple identical plants. Selection of desirable transgenics is made and new varieties are obtained and propagated vegetatively for commercial use. In seed propagated crops, mature transgenic plants can be self crossed to produce a homozygous inbred plant. The inbred plant produces seed containing the newly introduced heterologous nucleic acid. These seeds can be grown to produce plants that would produce the selected phenotype, (e.g., altered cell cycle content or composition).

Parts obtained from the regenerated plant, such as flowers, seeds, leaves, branches, fruit and the like are included in the invention, provided that these parts comprise cells comprising the isolated nucleic acid of the present invention. Progeny and variants, and mutants of the regenerated plants are also included within the scope of the invention, provided that these parts comprise the introduced nucleic acid sequences.

Transgenic plants expressing the selectable marker can be screened for transmission of the nucleic acid of the present invention by, for example, standard immunoblot and DNA detection techniques. Transgenic lines are also typically evaluated on levels of expression of the heterologous nucleic acid. Expression at the RNA level can be determined initially to identify and quantitate expression-positive plants. Standard techniques for RNA analysis can be employed and include PCR amplification assays using oligonucleotide primers designed to amplify only the heterologous RNA templates and solution hybridization assays using heterologous nucleic acid-specific probes. The RNA-positive plants can then analyzed for protein expression by Western immunoblot analysis using the specifically reactive antibodies of the present invention. In addition, in situ hybridization and immunocytochemistry according to standard protocols can be done using heterologous nucleic acid specific polynucleotide probes and antibodies, respectively, to localize sites of expression within transgenic tissue. Generally, a number of transgenic lines are usually screened for the incorporated nucleic acid to identify and select plants with the most appropriate expression profiles.

A preferred embodiment of the invention is a transgenic plant that is homozygous for the added heterologous nucleic acid; i.e., a transgenic plant that contains two added nucleic acid sequences, one gene at the same locus on each chromosome of a chromosome pair. A homozygous transgenic plant can be obtained by sexually mating (selfing) a heterozygous transgenic plant that contains a single added heterologous nucleic acid, germinating some of the seed produced and analyzing the resulting plants produced for altered cell division relative to a control plant (i.e., native, non-transgenic). Back-crossing to a parental plant and out-crossing with a non-transgenic plant are also contemplated.

The present invention also relates to transgenic plants and plant tissue comprising transgenic plant cells according to the invention. Due to the (over)expression of a CCP molecule, e.g., at developmental stages and/or in plant tissue in which they do not naturally occur, these transgenic plants may show various physiological, developmental and/or morphological modifications in comparison to wild-type plants.

Therefore, part of this invention is the use of the CCP molecules to modulate the cell cycle and/or plant cell division and/or growth in plant cells, plant tissues, plant organs and/or whole plants. To the scope of the invention also belongs a method for influencing the activity of CDKs such as CDC2a, or CDC2b, CKSs, CKIs, PLPs and KLPNTs in a plant cell by transforming the plant cell with a nucleic acid molecule according to the invention and/or manipulation of the expression of the molecule.

Furthermore, the invention also relates to a transgenic plant cell which contains (preferably stably integrated into its genome) a nucleic acid molecule of the invention or part thereof, wherein the transcription and/or expression of the nucleic acid molecule or part thereof leads to reduction of the synthesis of a CCP. In a preferred embodiment, the reduction is achieved by an anti-sense, sense, ribozyme, co-suppression and/or dominant mutant effect. The reduction of the synthesis of a protein according to the invention in the transgenic plant cells can result in an alteration in, e.g., cell division. In transgenic plants comprising such cells this can lead to various physiological, developmental and/or morphological changes.

In yet another aspect, the invention relates to harvestable parts and to propagation material of the transgenic plants of the invention which either contain transgenic plant cells expressing a nucleic acid molecule according to the invention or which contain cells which show a reduced level of the described protein. Harvestable parts can be in principle any useful parts of a plant, for example, flowers, pollen, seedlings, tubers, leaves, stems, fruit, seeds, roots etc. Propagation material includes, for example, seeds, fruits, cuttings, seedlings, tubers, rootstocks, and the like.

Transgenic Animals

As used herein, a “transgenic animal” is a non-human animal, preferably a mammal, more preferably a rodent such as a rat or mouse, in which one or more of the cells of the animal includes a transgene. Other examples of transgenic animals include non-human primates, sheep, dogs, cows, goats, chickens, amphibians, and the like. A transgene is exogenous DNA which is integrated into the genome of a cell from which a transgenic animal develops and which remains in the genome of the mature animal, thereby directing the expression of an encoded gene product in one or more cell types or tissues of the transgenic animal. As used herein, a “homologous recombinant animal” is a non-human animal, preferably a mammal, more preferably a mouse, in which an endogenous CCP gene has been altered by homologous recombination between the endogenous gene and an exogenous DNA molecule introduced into a cell of the animal, e.g., an embryonic cell of the animal, prior to development of the animal.

A transgenic animal of the invention can be created by introducing a CCP-encoding nucleic acid into the male pronuclei of a fertilized oocyte, e.g., by microinjection, retroviral infection, and allowing the oocyte to develop in a pseudopregnant female foster animal. The CCP cDNA sequence of SEQ ID NO:1-66 or 228-239 can be introduced as a transgene into the genome of a non-human animal. Alternatively, a nonhuman homologue of a human CCP gene, such as a mouse or rat CCP gene, can be used as a transgene. Alternatively, a CCP gene homologue, such as another CCP family member, can be isolated based on hybridization to the CCP cDNA sequences of SEQ ID NO:1-66 or 228-239 (described further in subsection I above) and used as a transgene. Intronic sequences and polyadenylation signals can also be included in the transgene to increase the efficiency of expression of the transgene. A tissue-specific regulatory sequence(s) can be operably linked to a CCP transgene to direct expression of a CCP protein to particular cells. Methods for generating transgenic animals via embryo manipulation and microinjection, particularly animals such as mice, have become conventional in the art and are described, for example, in U.S. Pat. Nos. 4,736,866 and 4,870,009, both by Leder et al., U.S. Pat. No. 4,873,191 by Wagner et al. and in Hogan, B., Manipulating the Mouse Embryo, (Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1986). Similar methods are used for production of other transgenic animals. A transgenic founder animal can be identified based upon the presence of a CCP transgene in its genome and/or expression of CCP mRNA in tissues or cells of the animals. A transgenic founder animal can then be used to breed additional animals carrying the transgene. Moreover, transgenic animals carrying a transgene encoding a CCP protein can further be bred to other transgenic animals carrying other transgenes.

V. Agricultural, Phytopharmaceutical and Pharmaceutical Compositions

The CCP nucleic acid molecules, CCP proteins, and anti-CCP antibodies (also referred to herein as “active compounds”) of the invention can be incorporated into compositions useful in agriculture and in plant cell and tissue culture. Plant protection compositions can be prepared by conventional means commonly used for the application of, for example, herbicides and pesticides. For example, certain additives known to those skilled in the art stabilizers or substances which facilitate the uptake by the plant cell, plant tissue or plant may be used.

The CCP nucleic acid molecules, CCP proteins, and anti-CCP antibodies (also referred to herein as “active compounds”) of the invention can also be incorporated into pharmaceutical compositions suitable for administration into animals. Such compositions typically comprise the nucleic acid molecule, protein, or antibody and a pharmaceutically acceptable carrier. As used herein the language “pharmaceutically acceptable carrier” is intended to include any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like, compatible with pharmaceutical administration. The use of such media and agents for pharmaceutically active substances is well known in the art. Except insofar as any conventional media or agent is incompatible with the active compound, use thereof in the compositions is contemplated. Supplementary active compounds can also be incorporated into the compositions.

The nucleic acid molecules of the invention can be inserted into vectors and used as gene therapy vectors. Gene therapy vectors can be delivered to a plant or subject by, for example, injection, local administration (see U.S. Pat. No. 5,328,470) or by stereotactic injection (see e.g., Chen et al. (1994) Proc. Natl. Acad. Sci. USA 91:3054-3057). The agricultural or pharmaceutical preparation of the gene therapy vector can include the gene therapy vector in an acceptable diluent, or can comprise a slow release matrix in which the gene delivery vehicle is imbedded. Alternatively, where the complete gene delivery vector can be produced intact from recombinant cells, e.g., retroviral vectors, the agricultural or pharmaceutical preparation can include one or more cells which produce the gene delivery system.

The agricultural and pharmaceutical compositions can be included in a container, pack, or dispenser together with instructions for administration.

VI. Uses and Methods of the Invention

The nucleic acid molecules, proteins, protein homologues, and antibodies described herein can be used in one or more of the following methods: a) agricultural uses (e.g., to increase plant yield and to develop phytopharmaceuticals); b) screening assays; c) predictive medicine (e.g., diagnostic assays, prognostic assays, monitoring clinical trials); d) methods of treatment (e.g., phytotherapeutic, therapeutic and prophylactic); e) transcriptomics; f) proteomics; g) metabolomics; h) ligandomics; and i) pharmacogenetics or pharmacogenomics. The isolated nucleic acid molecules of the invention can be used, for example, to express CCP protein (e.g., via a recombinant expression vector in a host cell or in gene therapy applications), to detect CCP mRNA (e.g., in a biological sample) or a genetic alteration in a CCP gene, and to modulate CCP activity, as described further below. The CCP proteins can be used to treat disorders characterized by insufficient or excessive production of a CCP substrate or production of CCP inhibitors. In addition, the CCP proteins can be used to screen for naturally occurring CCP substrates, to screen for drugs or compounds which modulate CCP activity, as well as to treat disorders characterized by insufficient or excessive production of CCP protein or production of CCP protein forms which have decreased or aberrant activity compared to CCP wild type protein. Moreover, the anti-CCP antibodies of the invention can be used to detect and isolate CCP proteins, regulate the bioavailability of CCP proteins, and modulate CCP activity.

A. Agricultural Uses:

In another embodiment of the invention, a method is provided for modifying cell fate and/or plant development and/or plant morphology and/or biochemistry and/or physiology comprising the modification of expression in particular cells, tissues or organs of a plant, of a genetic sequence encoding a CCP, e.g., a CCP operably connected with a plant-operable promoter sequence.

Modulation of the expression in a plant of a CCP or a homologue, analogue or derivative thereof as defined in the present invention can produce a range of desirable phenotypes in plants, such as, for example, the modification of one or more morphological, biochemical, or physiological characteristics including: (i) modification of the length of the G1 and/or the S and/or the G2 and/or the M phase of the cell cycle of a plant; (ii) modification of the G1/S and/or S/G2 and/or G2/M and/or M/G1 phase transition of a plant cell; (iii) modification of the initiation, promotion, stimulation or enhancement of cell division; (iv) modification of the initiation, promotion, stimulation or enhancement of DNA replication; (v) modification of the initiation, promotion, stimulation or enhancement of seed set and/or seed size and/or seed development; (vi) modification of the initiation, promotion, stimulation or enhancement of tuber formation; (vii) modification of the initiation, promotion, stimulation or enhancement of fruit formation; (viii) modification of the initiation, promotion, stimulation or enhancement of leaf formation; (ix) modification of the initiation, promotion, stimulation or enhancement of shoot initiation and/or development; (x) modification of the initiation, promotion, stimulation or enhancement of root initiation and/or development; (xi) modification of the initiation, promotion, stimulation or enhancement of lateral root initiation and/or development; (xii) modification of the initiation, promotion, stimulation or enhancement of nodule formation and/or nodule function; (xiii) modification of the initiation, promotion, stimulation or enhancement of the bushiness of the plant; (xiv) modification of the initiation, promotion, stimulation or enhancement of dwarfism in the plant; (xv) modification of the initiation, promotion, stimulation or enhancement of senescence; (xvi) modification of stem thickness and/or strength characteristics and/or wind-resistance of the stem and/or stem length; (xvii) modification of tolerance and/or resistance to biotic stresses such as pathogen infection; and (xviii) modification of tolerance and/or resistance to abiotic stresses such as drought stress or salt stress.

Methods to effect expression of a CCP or a homologue, analogue or derivative thereof as defined in the present invention in a plant cell, tissue or organ, include either the introduction of the protein directly to a cell, tissue or organ such as by microinjection of ballistic means or, alternatively, introduction of an isolated nucleic acid molecule encoding the protein into the cell, tissue or organ in an expressible format. Methods to effect expression of a CCP or a homologue, analogue or derivative thereof as defined in the current invention in whole plants include regeneration of whole plants from the transformed cells in which an isolated nucleic acid molecule encoding the protein was introduced in an expressible format.

The present invention clearly extends to any plant produced by the inventive method described herein, and any and all plant parts and propagules thereof. The present invention extends further to encompass the progeny derived from a primary transformed or transfected cell, tissue, organ or whole plant that has been produced by the inventive method, the only requirement being that the progeny exhibits the same genotypic and/or phenotypic characteristic(s) as those characteristic(s) that (have) been produced in the parent by the performance of the inventive method.

By “cell fate and/or plant development and/or plant morphology and/or biochemistry and/or physiology” is meant that one or more developmental and/or morphological and/or biochemical and/or physiological characteristics of a plant is altered by the performance of one or more steps pertaining to the invention described herein. “Cell fate” includes the cell-type or cellular characteristics of a particular cell that are produced during plant development or a cellular process therefor, in particular during the cell cycle or as a consequence of a cell cycle process.

The term “plant development” or the term “plant developmental characteristic” or similar terms shall, when used herein, be taken to mean any cellular process of a plant that is involved in determining the developmental fate of a plant cell, in particular the specific tissue or organ type into which a progenitor cell will develop. Cellular processes relevant to plant development will be known to those skilled in the art. Such processes include, for example, morphogenesis, photomorphogenesis, shoot development, root development, vegetative development, reproductive development, stem elongation, flowering, and regulatory mechanisms involved in determining cell fate, in particular a process or regulatory process involving the cell cycle.

The term “plant morphology” or the term “plant morphological characteristic” or similar term will, when used herein, be understood by those skilled in the art to include the external appearance of a plant, including any one or more structural features or combination of structural features thereof. Such structural features include the shape, size, number, position, color, texture, arrangement, and patternation of any cell, tissue or organ or groups of cells, tissues or organs of a plant, including the root, stem, leaf, shoot, petiole, trichome, flower, petal, stigma, style, stamen, pollen, ovule, seed, embryo, endosperm, seed coat, aleurone, fibre, fruit, cambium, wood, heartwood, parenchyma, aerenchyma, sieve element, phloem or vascular tissue.

The term “plant biochemistry” or the term “plant biochemical characteristic” or similar term will, when used herein, be understood by those skilled in the art to include the metabolic and catalytic processes of a plant, including primary and secondary metabolism and the products thereof, including any small molecules, macromolecules or chemical compounds, such as but not limited to starches, sugars, proteins, peptides, enzymes, hormones, growth factors, nucleic acid molecules, celluloses, hemicelluloses, calloses, lectins, fibres, pigments such as anthocyanins, vitamins, minerals, micronutrients, or macronutrients, that are produced by plants.

The term “plant physiology” or the term “plant physiological characteristic” or similar term will, when used herein, be understood to include the functional processes of a plant, including developmental processes such as growth, expansion and differentiation, sexual development, sexual reproduction, seed set, seed development, grain filling, asexual reproduction, cell division, dormancy, germination, light adaptation, photosynthesis, leaf expansion, fibre production, secondary growth or wood production, amongst others; responses of a plant to externally-applied factors such as metals, chemicals, hormones, growth factors, environment and environmental stress factors (e.g., anoxia, hypoxia, high temperature, low temperature, dehydration, light, daylength, flooding, salt, heavy metals, amongst others), including adaptive responses of plants to said externally-applied factors.

The CCP molecules of the present invention are useful in agriculture. The nucleic acid molecules, proteins, protein homologues, and antibodies described herein can be used to modulate the protein levels or activity of a protein involved in the cell cycle, e.g., proteins involved in the G1/S and/or the G2/M transition in the cell cycle due to environmental conditions, including abiotic stress such as cold, nutrient deprivation, heat, drought, salt stress, or biotic stress such as a pathogen attack.

Thus, the CCP molecules of the present invention may be used to modulate, e.g., enhance, crop yields; modulate, e.g., attenuate, stress, e.g. heat or nutrient deprivation; modulate tolerance to pests and diseases; modulate plant architecture; modulate plant quality traits; or modulate plant reproduction and seed development.

The CCP molecules of the present invention may also be used to modulate endoreduplication in storage cells, storage tissues, and/or storage organs of plants or parts thereof. The term “endoreduplication” includes recurrent DNA replication without consequent mitosis and cytokinesis. Preferred target storage organs and parts thereof for the modulation of endoreduplication are, for example, seeds (such as from cereals, oilseed crops), roots (such as in sugar beet), tubers (such as in potatoes) and fruits (such as in vegetables and fruit species). Increased endoreduplication in storage organs, and parts thereof, correlates with enhanced storage capacity and, thus, with improved yield. In another embodiment of the invention, the endoreduplication of a whole plant is modulated.

B. Screening Assays:

The invention provides a method (also referred to herein as a “screening assay”) for identifying modulators, i.e., candidate or test compounds or agents (e.g., peptides, peptidomimetics, small molecules or other drugs) which bind to CCP proteins, have a stimulatory or inhibitory effect on, for example, CCP expression or CCP activity, or have a stimulatory or inhibitory effect on, for example, the expression or activity of a CCP substrate.

In one embodiment, the invention provides assays for screening candidate or test compounds which are substrates of a CCP protein or polypeptide or biologically active portion thereof. In another embodiment, the invention provides assays for screening candidate or test compounds which bind to or modulate the activity of a CCP protein or polypeptide or biologically active portion thereof, e.g., modulate the ability of CCP to interact with its cognate ligand. The test compounds of the present invention can be obtained using any of the numerous approaches in combinatorial library methods known in the art, including: biological libraries; spatially addressable parallel solid phase or solution phase libraries; synthetic library methods requiring deconvolution; the ‘one-bead one-compound’ library method; and synthetic library methods using affinity chromatography selection. The biological library approach is limited to peptide libraries, while the other four approaches are applicable to peptide, non-peptide oligomer or small molecule libraries of compounds (Lam, K. S. (1997) Anticancer Drug Des. 12:145).

Examples of methods for the synthesis of molecular libraries can be found in the art, for example in: DeWitt et al. (1993) Proc. Natl. Acad. Sci. U.S.A. 90:6909; Erb et al. (1994) Proc. Natl. Acad. Sci. USA 91:11422; Zuckeimann et al. (1994). J. Med. Chem. 37:2678; Cho et al. (1993) Science 261:1303; Carrell et al. (1994) Angew. Chem. Int. Ed. Engl. 33:2059; Carell et al. (1994) Angew. Chem. Int. Ed. Engl. 33:2061; and in Gallop et al. (1994) J. Med. Chem. 37:1233.

Libraries of compounds may be presented in solution (e.g., Houghten (1992) Biotechniques 13:412-421), or on beads (Lam (1991) Nature 354:82-84), chips (Fodor (1993) Nature 364:555-556), bacteria (Ladner U.S. Pat. No. 5,223,409), spores (Ladner U.S. Pat. No. '409), plasmids (Cull et al. (1992) Proc Natl Acad Sci USA 89:1865-1869) or on phage (Scott and Smith (1990) Science 249:386-390); (Devlin (1990) Science 249:404-406); (Cwirla et al. (1990) Proc. Natl. Acad. Sci. 87:6378-6382); (Felici (1991) J. Mol. Biol. 222:301-310); (Ladner supra.).

In another embodiment, an assay is a cell-based assay comprising contacting a cell expressing a CCP target molecule (e.g., a plant cyclin dependent kinase) with a test compound and determining the ability of the test compound to modulate (e.g. stimulate or inhibit) the activity of the CCP target molecule. Determining the ability of the test compound to modulate the activity of a CCP target molecule can be accomplished, for example, by determining the ability of the CCP protein to bind to or interact with the CCP target molecule, or by determining the ability of the target molecule, e.g., the plant cyclin dependent kinase, to phosphorylate a protein.

The ability of the target molecule, e.g., the plant cyclin dependent kinase, to phosphorylate a protein can be determined by, for example, an in vitro kinase assay. Briefly, a protein can be incubated with the target molecule, e.g., the plant cyclin dependent kinase, and radioactive ATP, e.g., [γ-³²P] ATP, in a buffer containing MgCl₂ and MnCl₂, e.g., 10 mM MgCl₂ and 5 mM MnCl₂. Following the incubation, the immunoprecipitated protein can be separated by SDS-polyacrylamide gel electrophoresis under reducing conditions, transferred to a membrane, e.g., a PVDF membrane, and autoradiographed. The appearance of detectable bands on the autoradiograph indicates that the protein has been phosphorylated. Phosphoaminoacid analysis of the phosphorylated substrate can also be performed in order to determine which residues on the protein are phosphorylated. Briefly, the radiophosphorylated protein band can be excised from the SDS gel and subjected to partial acid hydrolysis. The products can then be separated by one-dimensional electrophoresis and analyzed on, for example, a phosphoimager and compared to ninhydrin-stained phosphoaminoacid standards.

Determining the ability of the CCP protein to bind to or interact with a CCP target molecule can be accomplished by determining direct binding. Determining the ability of the CCP protein to bind to or interact with a CCP target molecule can be accomplished, for example, by coupling the CCP protein with a radioisotope or enzymatic label such that binding of the CCP protein to a CCP target molecule can be determined by detecting the labeled CCP protein in a complex. For example, CCP molecules, e.g., CCP proteins, can be labeled with ¹²⁵I, ³⁵S, ¹⁴C, or ³H, either directly or indirectly, and the radioisotope detected by direct counting of radioemmission or by scintillation counting. Alternatively, CCP molecules can be enzymatically labeled with, for example, horseradish peroxidase, alkaline phosphatase, or luciferase, and the enzymatic label detected by determination of conversion of an appropriate substrate to product.

It is also within the scope of this invention to determine the ability of a compound to modulate the interaction between CCP and its target molecule, without the labeling of any of the interactants. For example, a microphysiometer can be used to detect the interaction of CCP with its target molecule without the labeling of either CCP or the target molecule. McConnell, H. M. et al. (1992) Science 257:1906-1912. As used herein, a “microphysiometer” (e.g., Cytosensor) is an analytical instrument that measures the rate at which a cell acidifies its environment using a light-addressable potentiometric sensor (LAPS). Changes in this acidification rate can be used as an indicator of the interaction between compound and receptor.

In a preferred embodiment, determining the ability of the CCP protein to bind to or interact with a CCP target molecule can be accomplished by determining the activity of the target molecule. For example, the activity of the target molecule can be determined by detecting induction of a cellular second messenger of the target (e.g., intracellular Ca²⁺, diacylglycerol, IP₃, etc.), detecting catalytic/enzymatic activity of the target an appropriate substrate, detecting the induction of a reporter gene (comprising a target-responsive regulatory element operatively linked to a nucleic acid encoding a detectable marker, e.g., chloramphenicol acetyl transferase), or detecting a target-regulated cellular response.

In yet another embodiment, an assay of the present invention is a cell-free assay in which a CCP protein or biologically active portion thereof is contacted with a test compound and the ability of the test compound to bind to the CCP protein or biologically active portion thereof is determined. Binding of the test compound to the CCP protein can be determined either directly or indirectly as described above. In a preferred embodiment, the assay includes contacting the CCP protein or biologically active portion thereof with a known compound which binds CCP to form an assay mixture, contacting the assay mixture with a test compound, and determining the ability of the test compound to interact with a CCP protein, wherein determining the ability of the test compound to interact with a CCP protein comprises determining the ability of the test compound to preferentially bind to CCP or biologically active portion thereof as compared to the known compound.

In another embodiment, the assay is a cell-free assay in which a CCP protein or biologically active portion thereof is contacted with a test compound and the ability of the test compound to modulate (e.g., stimulate or inhibit) the activity of the CCP protein or biologically active portion thereof is determined. Determining the ability of the test compound to modulate the activity of a CCP protein can be accomplished, for example, by determining the ability of the CCP protein to bind to a CCP target molecule by one of the methods described above for determining direct binding. Determining the ability of the CCP protein to bind to a CCP target molecule can also be accomplished using a technology such as real-time Biomolecular Interaction Analysis (BIA). Sjolander, S, and Urbaniczky, C. (1991) Anal. Chem. 63:2338-2345 and Szabo et al. (1995) Curr. Opin. Struct. Biol. 5:699-705. As used herein, “BIA” is a technology for studying biospecific interactions in real time, without labeling any of the interactants (e.g., BIAcore). Changes in the optical phenomenon of surface plasmon resonance (SPR) can be used as an indication of real-time reactions between biological molecules.

In an alternative embodiment, determining the ability of the test compound to modulate the activity of a CCP protein can be accomplished by determining the ability of the CCP protein to further modulate the activity of a CCP target molecule (e.g., a CCP mediated signal transduction pathway component). For example, the activity of the effector molecule on an appropriate target can be determined, or the binding of the effector to an appropriate target can be determined as previously described.

In yet another embodiment, the cell-free assay involves contacting a CCP protein or biologically active portion thereof with a known compound which binds the CCP protein to form an assay mixture, contacting the assay mixture with a test compound, and determining the ability of the test compound to interact with the CCP protein, wherein determining the ability of the test compound to interact with the CCP protein comprises determining the ability of the CCP protein to preferentially bind to or modulate the activity of a CCP target molecule.

The cell-free assays of the present invention are amenable to use of both soluble and/or membrane-bound forms of proteins (e.g., CCP proteins or biologically active portions thereof). In the case of cell-free assays in which a membrane-bound form a protein is used it may be desirable to utilize a solubilizing agent such that the membrane-bound form of the protein is maintained in solution. Examples of such solubilizing agents include non-ionic detergents such as n-octylglucoside, n-dodecylglucoside, n-dodecylmaltoside, octanoyl-N-methylglucamide, decanoyl-N-methylglucamide, Triton® X-100, Triton® X-114, Thesit®, Isotridecypoly(ethylene glycol ether)_(n), 3-[(3-cholamidopropyl)dimethylamminio]-1-propane sulfonate (CHAPS), 3-[(3-cholamidopropyl)dimethylamminio]-2-hydroxy-1-propane sulfonate (CHAPSO), or N-dodecyl=N,N-dimethyl-3-ammonio-1-propane sulfonate.

In more than one embodiment of the above assay methods of the present invention, it may be desirable to immobilize either CCP or its target molecule to facilitate separation of complexed from uncomplexed forms of one or both of the proteins, as well as to accommodate automation of the assay. Binding of a test compound to a CCP protein, or interaction of a CCP protein with a target molecule in the presence and absence of a candidate compound, can be accomplished in any vessel suitable for containing the reactants. Examples of such vessels include microtitre plates, test tubes, and micro-centrifuge tubes. In one embodiment, a fusion protein can be provided which adds a domain that allows one or both of the proteins to be bound to a matrix. For example, glutathione-S-transferase/CCP fusion proteins or glutathione-S-transferase/target fusion proteins can be adsorbed onto glutathione sepharose beads (Sigma Chemical, St. Louis, Mo.) or glutathione derivatized microtitre plates, which are then combined with the test compound or the test compound and either the non-adsorbed target protein or CCP protein, and the mixture incubated under conditions conducive to complex formation (e.g., at physiological conditions for salt and pH). Following incubation, the beads or microtitre plate wells are washed to remove any unbound components, the matrix immobilized in the case of beads, complex determined either directly or indirectly, for example, as described above. Alternatively, the complexes can be dissociated from the matrix, and the level of CCP binding or activity determined using standard techniques.

Other techniques for immobilizing proteins on matrices can also be used in the screening assays of the invention. For example, either a CCP protein or a CCP target molecule can be immobilized utilizing conjugation of biotin and streptavidin. Biotinylated CCP protein or target molecules can be prepared from biotin-NHS (N-hydroxy-succinimide) using techniques well known in the art (e.g., biotinylation kit, Pierce Chemicals, Rockford, Ill.), and immobilized in the wells of streptavidin-coated 96 well plates (Pierce Chemical). Alternatively, antibodies reactive with CCP protein or target molecules but which do not interfere with binding of the CCP protein to its target molecule can be derivatized to the wells of the plate, and unbound target or CCP protein trapped in the wells by antibody conjugation. Methods for detecting such complexes, in addition to those described above for the GST-immobilized complexes, include immunodetection of complexes using antibodies reactive with the CCP protein or target molecule, as well as enzyme-linked assays which rely on detecting an enzymatic activity associated with the CCP protein or target molecule.

In another embodiment, modulators of CCP expression are identified in a method wherein a cell is contacted with a candidate compound and the expression of CCP mRNA or protein in the cell is determined. The level of expression of CCP mRNA or protein in the presence of the candidate compound is compared to the level of expression of CCP mRNA or protein in the absence of the candidate compound. The candidate compound can then be identified as a modulator of CCP expression based on this comparison. For example, when expression of CCP mRNA or protein is greater (statistically significantly greater) in the presence of the candidate compound than in its absence, the candidate compound is identified as a stimulator of CCP mRNA or protein expression. Alternatively, when expression of CCP mRNA or protein is less (statistically significantly less) in the presence of the candidate compound than in its absence, the candidate compound is identified as an inhibitor of CCP mRNA or protein expression. The level of CCP mRNA or protein expression in the cells can be determined by methods described herein for detecting CCP mRNA or protein.

In yet another aspect of the invention, the CCP proteins can be used as “bait proteins” in a two-hybrid assay or three-hybrid assay (see, e.g., U.S. Pat. No. 5,283,317; Zervos et al. (1993) Cell 72:223-232; Madura et al. (1993). J. Biol. Chem. 268:12046-12054; Bartel et al. (1993) Biotechniques 14:920-924; Iwabuchi et al. (1993) Oncogene 8:1693-1696; and Brent WO94/10300), to identify other proteins, which bind to or interact with CCP (“CCP-binding proteins” or “CCP-bp”) and are involved in CCP activity. Such CCP-binding proteins are also likely to be involved in the propagation of signals by the CCP proteins or CCP targets as, for example, downstream elements of a CCP-mediated signaling pathway. Alternatively, such CCP-binding proteins are likely to be CCP inhibitors. Alternatively, a mammalian two-hybrid system can be used which includes e.g. a chimeric green fluorescent protein encoding reporter gene (Shioda et al. 2000, Proc. Natl. Acad. Sci. USA 97, 5520-5224). Yet another alternative consists of a bacterial two-hybrid system using e.g. HIS as reporter gene (Joung et al. 2000, Proc. Natl. Acad. Sci. USA 97, 7382-7387).

The two-hybrid system is based on the modular nature of most transcription factors, which consist of separable DNA-binding and activation domains. Briefly, the assay utilizes two different DNA constructs. In one construct, the gene that codes for a CCP protein is fused to a gene encoding the DNA binding domain of a known transcription factor (e.g., GAL-4). In the other construct, a DNA sequence, from a library of DNA sequences, that encodes an unidentified protein (“prey” or “sample”) is fused to a gene that codes for the activation domain of the known transcription factor. If the “bait” and the “prey” proteins are able to interact, in vivo, forming a CCP-dependent complex, the DNA-binding and activation domains of the transcription factor are brought into close proximity. This proximity allows transcription of a reporter gene (e.g., LacZ) which is operably linked to a transcriptional regulatory site responsive to the transcription factor. Expression of the reporter gene can be detected and cell colonies containing the functional transcription factor can be isolated and used to obtain the cloned gene which encodes the protein which interacts with the CCP protein.

This invention further pertains to novel agents identified by the above-described screening assays. Accordingly, it is within the scope of this invention to further use an agent identified as described herein in an appropriate plant or animal model. For example, an agent identified as described herein (e.g., a CCP modulating agent, an antisense CCP nucleic acid molecule, a CCP-specific antibody, or a CCP-binding partner) can be used in a plant or animal model to determine the efficacy, toxicity, or side effects of treatment with such an agent. Alternatively, an agent identified as described herein can be used in a plant or animal model to determine the mechanism of action of such an agent. Furthermore, this invention pertains to uses of novel agents identified by the above-described screening assays for the agricultural and therapeutic uses described herein.

C. Detection Assays

Portions or fragments of the cDNA sequences identified herein (and the corresponding complete gene sequences) can be used in numerous ways as polynucleotide reagents. For example, these sequences can be used to: map their respective genes on a chromosome; and, thus, locate gene regions associated with genetic disease; identify an individual from a minute biological sample (tissue typing); and aid in forensic identification of a biological sample. Once the sequence (or a portion of the sequence) of a gene has been isolated, this sequence can be used to map the location of the gene on a chromosome. This process is called chromosome mapping. Accordingly, portions or fragments of the CCP nucleotide sequences, described herein, can be used to map the location of the CCP genes on a chromosome. The mapping of the CCP sequences to chromosomes is an important first step in correlating these sequences with genes associated with disease.

Briefly, CCP genes can be mapped to chromosomes by preparing PCR primers (preferably 15-25 bp in length) from the CCP nucleotide sequences. Computer analysis of the CCP sequences can be used to predict primers that do not span more than one exon in the genomic DNA, thus complicating the amplification process. These primers can then be used for PCR screening of cell hybrids containing individual plant or human chromosomes. Only those hybrids containing the plant or human gene corresponding to the CCP sequences will yield an amplified fragment.

Other mapping strategies which can similarly be used to map a CCP sequence to its chromosome include in situ hybridization (described in Fan, Y. et al. (1990) Proc. Natl. Acad. Sci. USA, 87:6223-27), pre-screening with labeled flow-sorted chromosomes, and pre-selection by hybridization to chromosome specific cDNA libraries.

Fluorescence in situ hybridization (FISH) of a DNA sequence to a metaphase chromosomal spread can further be used to provide a precise chromosomal location in one step. Chromosome spreads can be made using cells whose division has been blocked in metaphase by a chemical such as colcemid that disrupts the mitotic spindle. The chromosomes can be treated briefly with trypsin, and then stained with Giemsa. A pattern of light and dark bands develops on each chromosome, so that the chromosomes can be identified individually. The FISH technique can be used with a DNA sequence as short as 500 or 600 bases. However, clones larger than 1,000 bases have a higher likelihood of binding to a unique chromosomal location with sufficient signal intensity for simple detection. Preferably 1,000 bases, and more preferably 2,000 bases will suffice to get good results at a reasonable amount of time. For a review of this technique, see Verma et al., Human Chromosomes: A Manual of Basic Techniques (Pergamon Press, New York 1988).

Reagents for chromosome mapping can be used individually to mark a single chromosome or a single site on that chromosome, or panels of reagents can be used for marking multiple sites and/or multiple chromosomes. Reagents corresponding to noncoding regions of the genes actually are preferred for mapping purposes. Coding sequences are more likely to be conserved within gene families, thus increasing the chance of cross hybridizations during chromosomal mapping.

Once a sequence has been mapped to a precise chromosomal location, the physical position of the sequence on the chromosome can be correlated with genetic map data. (Such data are found, for example, in V. McKusick, Mendelian Inheritance in Man, available on-line through Johns Hopkins University Welch Medical Library). The relationship between a gene and a disease, mapped to the same chromosomal region, can then be identified through linkage analysis (co-inheritance of physically adjacent genes), described in, for example, Egeland, J. et al. (1987) Nature, 325:783-787.

Moreover, differences in the DNA sequences between plants affected and unaffected with a disease associated with the CCP gene, can be determined. If a mutation is observed in some or all of the affected plants but not in any unaffected plants, then the mutation is likely to be the causative agent of the particular disease. Comparison of affected and unaffected plants generally involves first looking for structural alterations in the chromosomes, such as deletions or translocations that are visible from chromosome spreads or detectable using PCR based on that DNA sequence. Ultimately, complete sequencing of genes from several plants can be performed to confirm the presence of a mutation and to distinguish mutations from polymorphisms.

D. Predictive Medicine:

The present invention also pertains to the field of predictive medicine in which diagnostic assays, prognostic assays, and monitoring clinical trials are used for prognostic (predictive) purposes to thereby treat an individual prophylactically. Accordingly, one aspect of the present invention relates to diagnostic assays for determining CCP protein and/or nucleic acid expression as well as CCP activity, in the context of a biological sample (e.g., blood, serum, cells, tissue) to thereby determine whether an individual is afflicted with a disease or disorder, or is at risk of developing a disorder, associated with aberrant CCP expression or activity. The invention also provides for prognostic (or predictive) assays for determining whether an individual is at risk of developing a disorder associated with CCP protein, nucleic acid expression or activity. For example, mutations in a CCP gene can be assayed in a biological sample. Such assays can be used for prognostic or predictive purpose to thereby phophylactically treat an individual prior to the onset of a disorder characterized by or associated with CCP protein, nucleic acid expression or activity.

Another aspect of the invention pertains to monitoring the influence of agents (e.g., drugs, compounds) on the expression or activity of CCP in clinical trials.

E. Methods of Treatment:

The present invention provides for both prophylactic and therapeutic methods of treating a subject at risk of (or susceptible to) a disorder or having a disorder associated with aberrant CCP expression or activity. With regards to both prophylactic and therapeutic methods of treatment, such treatments may be specifically tailored or modified, based on knowledge obtained from the field of pharmacogenomies. “Pharmacogenomics”, as used herein, refers to the application of genomics technologies such as gene sequencing, statistical genetics, and gene expression analysis to drugs in clinical development and on the market. More specifically, the term refers the study of how a patient's genes determine his or her response to a drug (e.g., a patient's “drug response phenotype”, or “drug response genotype”.) Thus, another aspect of the invention provides methods for tailoring an individual's prophylactic or therapeutic treatment with either the CCP molecules of the present invention or CCP modulators according to that individual's drug response genotype. Pharmacogenomics allows a clinician or physician to target prophylactic or therapeutic treatments to patients who will most benefit from the treatment and to avoid treatment of patients who will experience toxic drug-related side effects.

This invention is further illustrated by the following examples which should not be construed as limiting. The contents of all references, patents and published patent applications cited throughout this application, as well as the Figures and the Sequence Listing are incorporated herein by reference.

EXAMPLES Example 1 Identification of Plant CCP Polypeptides Using the Two Hybrid System with CDC2B as a Bait

A two-hybrid screening was performed using as bait a fusion between the GAL4 DNA-binding domain and one of the following: CDC2bAt.N161 (GenBank accession number D10851; residue Asp161 converted into Asn161); CKS1At (GenBank accession number AJ000016); E2Fa (=E2F5) (GenBank accession number AJ294534) dimerization domain (226-356aa; SEQ ID NO:205); CKI4 (SEQ ID NO:264); PLP1 (GenBank accession number T01601); KLPNT1 (GenBank accession number AB011479; protein ID number BAB11568) motor domain (36-508 aa); KLPNT1 (GenBank accession number AB011479; protein ID number BAB11568) stalk domain (427-867 aa); KLPNT2=TH65 (GenBank accession number AJ001729) neck domain (3-186 aa); KLPNT2=TH65 (GenBank accession number AJ001729) stalk domain (73-608 aa); E2Fb (=E2F3) (GenBank accession number AJ294533) N-terminal domain (1-385 aa; SEQ ID NO:206), respectively

CDC2bAt.N161 is a dominant negative form of the CDC2bAt protein. The D161 residue in CDC2bAt is crucial for ATP binding and, thus, the mutation of this residue results in an inactive kinase. The interactions between this mutated CDK and its substrates and regulatory proteins are also more stabilised as a result of this mutation.

In yeast the PHO genes are part of a complex regulatory network linking phosphate availability with the expression of phosphatases. When phosphate levels are high the PHO80/PHO85 cyclin/CDK complex phosphorylates a transcription factor. This transcription factor of phosphatase genes thereby becomes inactive. The S. cerevisiae PHO85 protein can interact with the G1 specific cyclins PCL1 and PCL2 (close homologues to the PHO80). In a yeast strain deficient for the G1 cyclins CLN1 and CLN2, PHO80 is required for G1 progression. This result suggests that PHO85 is involved in a regulatory pathway that links the nutrient status of the cell with cell division activity. The five PLP of A. thaliana show similarity to the yeast cyclin-like PHO80 gene.

Kinesins use the cytoskeleton to move around vesicles, organelles, chromosomes and the like in the cell. They can also be involved in spindle formation. Kinesins consist of three functional unrelated domains: the motor domain (involved in microtubule binding; contains the ATPase domain), the stalk region (involved in homo- or heterodimirisation of the kinesins), and the tail (involved in the interaction with the ‘substrates’ of the kinesin). Two hybrid screens were performed using different parts of two-kinesin-related proteins (KLPNT1 and KLPNT2 (being more than 80% identical to KLPNT1). Other information obtained by the two hybrid approach is the dimerization of the kinesins: the KLPNT1 and KLPNT2 interact (stalks and stalks-tail) with and between themselves.

Vectors and strains used were provided with the Matchmaker Two-Hybrid System (Clontech, Palo Alto, Calif.). The bait was constructed by inserting the CDC2bAt.N161 (GenBank accession number D10851; residue Asp161 converted into Asn161); CKS1At (GenBank accession number AJ000016); E2Fa (=E2F5) (GenBank accession number AJ294534) dimerization domain (226-356aa; SEQ ID NO:205); CKI4 (SEQ ID NO:264); PLP1 (GenBank accession number T01601); KLPNT1 (GenBank accession number AB011479; protein ID number BAB11568) motor domain (36-508 aa); KLPNT1 (GenBank accession number AB011479; protein ID number BAB11568) stalk domain (427-867 aa); KLPNT2=TH65 (GenBank accession number AJ001729) neck domain (3-186 aa); KLPNT2=TH65 (GenBank accession number AJ001729) stalk domain (73-608 aa); E2Fb (=E2F3) (GenBank accession number AJ294533) N-terminal domain (1-385 aa; SEQ ID NO:206), respectively, into the pGBT9 vector. Bait vectors where constructed by introducing the PCR fragment created from the corresponding cDNA using primers to incorporate EcoRI and BamH1 restriction enzyme sites. The PCR fragment was cut with EcoRI and BamH1 and cloned into the EcoRI and BamH1 sites of pGBT9, resulting in the desired plasmid. The GAL4 activation domain cDNA fusion library was constructed as described in De Veylder et al 1999, 208(4) p453-62 from mRNA of Arabidopsis thaliana cell suspensions harvested at various growing stages: early exponential, exponential, early stationary, and stationary phase.

For the screening a 1-liter culture of the Saccharomyces cerevisiae strain HF7c (MATaura3-52 his3-200 ade2-101 lys2-801 trp1-901 leu2-3,112 gal4-542 gal80-538 LYS2::GAL1_(UAS)-GAL1_(TATA)-HIS3 URA3::GAL4_(17mers(3x))-CyC1_(TATA)-LacZ) was sequentially transformed with the bait plasmid and 20 μg DNA of the library using the lithium acetate method (Geitz et al. (1992) supra). To estimate the number of independent cotransformants, 1/1000 of the transformation mix was plated on Leu- and Trp-medium. The rest of the transformation mix was plated on medium to select for histidine prototrophy (Tip-, Leu-, His-). After 5 days of growth at 30° C., the colonies larger than 2 mm were streaked on histidine-lacking medium. At total for each screening at least 10⁷ independent cotransformants were screened for there ability to grow on histidine free medium. Of the His⁺ colonies the activation domain plasmids were isolated as described (Hoffman and Winston, 1987, Gene 57, 267-272). The hybriZAP™ inserts were PCR amplified and the PCR fragments were digested with AluI and fractionized on a 2% agarose gel. Plasmid DNA of which the inserts gave rise to different restriction patterns were electroporated into Escherichia coli XL1-Blue, and the DNA sequence of the inserts was determined. Extracted DNA was also used to retransform HF7c to test the specificity of the interaction.

Using the foregoing technique, 61 cDNAs were identified, their sequences were determined and found to contain open reading frames termed CCP1 through CCP61 (FIGS. 1-61).

Example 2 Extension of CCP Encoding Polynucleotides to Full Length or to Recover Regulatory Elements

The CCP encoding nucleic acid sequences (SEQ ID NO:1-66 or 228-239) are used to design oligonucleotide primers for extending a partial nucleotide sequence to full length or for obtaining 5′ sequences from genomic or cDNA libraries. One primer is synthesized to initiate extension in the antisense direction (XLR) and the other is synthesized to extend sequence in the sense direction (XLF). Primers allow the extension of the known CCP encoding sequence “outward” generating amplicons containing new, unknown nucleotide sequence for the region of interest. The initial primers are designed from the cDNA using OLIGO® 4.06 Primer Analysis Software (National Biosciences), or another appropriate program, to be preferably 22-30 nucleotides in length, to have a GC content of preferably 50% or more, and to anneal to the target sequence at temperatures preferably about 68°-72° C. Any stretch of nucleotides which would result in hairpin structures and primer-primer dimerizations is avoided. The original, selected cDNA libraries, prepared from mRNA isolated from actively dividing cells or a plant genomic library are used to extend the sequence; the latter is most useful to obtain 5′ upstream regions. If more extension is necessary or desired, additional sets of primers are designed to further extend the known region.

Sense XLF primers can also be designed based on publicly available genomic sequences. GENEMARK.hmm (hidden morkov model) version 2.2a software (default parameters) can e.g. be used to predict open reading frames. The 5′ end of the predicted open reading frame is then subsequently used to design the sense XLF primer. Said XLF primer and the appropriate XLR primer are then used in an RT-PCR (reverse transcription-polymerase chain reaction) reaction to amplify the predicted cDNA. The resulting PCR product is cloned in a suitable vector and subjected to DNA sequence analysis to verify the prediction.

Primers used to amplify coding regions of the CCPs of the invention are designed such that the PCR product can be cloned in the pDONR201 vector (Gateway™ cloning system, Invitrogen). Thus, a sense primer has the attB1 site (SEQ ID NO:246) at its 5′ end. For current purposes, the attB1 site is followed by a consensus Kozak sequence (SEQ ID NO:247; Kozak (1989)J Cell Biol 108:229-241; Lütck et al. (1987) EMBO J. 6:43-48). The 3′ end of the sense primer comprises the gene-specific parts as indicated in FIGS. 1-46. An antisense primer has at the 5′ end the attB2 site (SEQ ID NO:248) followed by the inverse complement of the gene/coding region of interest as indicated in FIGS. 1-46. Primers used for CCP amplification by PCR are given with their SEQ ID NOs in Table 3. The sequence of cloned CCP PCR products was or is determined using the sense primer prm1024 (SEQ ID NO:265) and the antisense primer prm1025 (SEQ ID NO:266).

TABLE III sense antisense primer primer CCP PCR primers SEQ ID SEQ ID Molecule sense + antisense NO: NO: CCP1 prm0733 + prm0734 133 134 CCP2 prm0663 + prm0664 135 136 CCP3 prm0705 + prm0706 137 138 CCP4 prm0659 + prm0660 139 140 CCP5 prm0749 + prm0750 141 142 CCP6 prm0707 + prm0708 143 144 CCP7/8 prm0657 + prm0658 145 146 CCP9 prm0582 + prm0583 147 148 CCP10 prm0671 + prm0672 149 150 CCP11 prm0729 + prm0730 151 152 CCP12 + prm1676 + prm1677 153 154 CCP13 CCP14 prm0701 + prm0702 155 156 CCP15 prm0445 + prm0446 157 158 CCP16 prm0321 + prm0322 159 160 CCP17 prm0632 + prm0633 161 162 CCP18 prm0488 + prm0489 163 164 CCP19 prm0661 + prm0662 165 166 CCP20 + prm0709 + prm0710 167 168 CCP21 CCP22 prm0711 + prm0712 169 170 CCP23 prm0819 + prm0820 171 172 CCP24 prm0739 + prm0740 173 174 CCP25 prm0741 + prm0742 175 176 CCP26 prm0703 + prm0704 177 178 CCP27 prm0817 + prm0818 179 180 CCP28 prm0713 + prm0714 181 182 CCP29 / / / CCP30 prm0480 + prm0481 183 184 CCP31 prm0737 + prm0738 185 186 CCP32 prm1493 + prm1494 187 188 CCP33 prm0319 + prm0320 189 190 CCP34 prm1377 + prm1378 191 192 CCP35 prm1381 + prm1382 193 194 CCP36 / / / CCP37 prm1379 + prm1380 195 196 CCP38 prm1383 + prm1384 197 198

By following the instructions for the XL-PCR kit (Perkin Elmer) and thoroughly mixing the enzyme and reaction mix, high fidelity amplification is obtained. Beginning with 40 pmol of each primer and the recommended concentrations of all other components of the kit, PCR is performed suing the Peltier Thermal Cycle (PTC200; MJ Research, Watertown Mass.) and the following parameters:

Step 1 94° C. for 1 min (initial denaturation) Step 2 65° C. for 1 min Step 3 68° C. for 6 min Step 4 94° for 15 sec Step 5 65° C. for 1 min Step 6 68° C. for 7 min Step 7 Repeat steps 4-6 for 15 additional cycles Step 8 94° C. for 15 sec Step 9 65° C. for 1 min Step 10 68° C. for 7:15 min Step 11 Repeat step 8-10 for 12 cycles Step 12 72° C. for 8 min Step 13 4° C. (and holding)

A 5-10 μl aliquot of the reaction mixture is analyzed by electrophoresis on a low concentration (about 0.6-0.8%) agarose mini-gel to determine which reactions were successful in extending the sequence. Bands thought to contain the largest products were selected and cut out of the gel. Further purification involves using a commercial gel extraction method such as QIAQuick™ (QIAGEN Inc). After recovery of the DNA, Klenow enzyme was used to trim single-stranded, nucleotide overhangs creating blunt ends which facilitate religation and cloning. After ethanol precipitation, the products are redissolved in 13 μl of ligation buffer, 1 μl T4-DNA ligase (15 units) and 1 μl T4 polynucleotide kinase are added, and the mixture is incubated at room temperature for 2-3 hours or overnight at 16° C. Competent E. coli cells (in 40 μl of appropriate media) are transformed with 3 μl of ligation mixture and cultured in 80 μl of SOC medium (Sambrook, supra). After incubation for one hour at 37° C., the whole transformation mixture is plated on Luria Bertani (LB)-agar (Sambrook, supra) containing 2×Carb. The following day, several colonies are randomly picked from each plate and cultured in 150 p. 1 of liquid LB/2×Carb medium placed in an individual well of an appropriate, commerically-available, sterile 96-well microtiter plate. The following day, 5 μl of each overnight culture is transferred into a non-sterile 96-well plate and after dilution 1:10 with water, 5 μl of each sample is transferred into a PCR array. For PCR amplification, 18 μl of concentrated PCR reaction mix (3.3×) containing 4 units of 4Tth DNA polymerase, a vector primer and both of the gene specific primers used for the extension reaction are added to each well. Amplification is performed using the following conditions:

Step 1 94° C. for 60 sec Step 2 94° C. for 20 sec Step 3 55° C. for 30 sec Step 4 72° C. for 90 sec Step 5 Repeat steps 2-4 for an additional 29 cycles Step 6 72° C. for 180 sec Step 7 4° C. (and holding) Aliquots of the PCR reactions are run on agarose gels together with molecular weight markers. The sizes of the PCR products are compared to the original partial cDNAs, and appropriate clones are selected, ligated into plasmid and sequenced.

Example 3 Expression of Recombinant CCP Proteins in Transgenic Plants

In this example, the CCP molecules of the present invention were expressed in a 35S expression vector in transgenic plants. The CCP molecules of this invention were cloned using standard cloning procedures between a suitable promoter, e.g. the CaMV35S promoter or any promoter from e.g. Table II, and a suitable terminator, e.g., the NOS 3′ untranslated region. The resulting recombinant gene is subsequently cloned in a suitable binary vector and the resulting plant transformation vector is then transferred to Agrobacterium tumefaciens. Arabidopsis thaliana is transformed with this Agrobacterium applying the in planta flower-dip transformation method (Clough and Bent, Plant J. 16:735-743, 1998). Transgenic plant lines are selected on a growth medium containing the suitable selection agent (e.g., kanamycin or Basta) or on the basis of scoring the expression of a screenable marker (e.g., luciferase, green fluorescent protein).

For tissue-specific expression, the CCP gene can also be expressed under control of the minimal 35S promoter containing UAS elements. These UAS elements are sites for transcriptional activation by the GAL4-VP16 fusion protein. The GAL4-VP16 fusion protein in turn is expressed under control of a tissue-specific promoter. The UAS-CCP construct and the GAL4-VP16 construct are combined by co-transformation of both constructs, subsequent transformation of single constructs or by sexual cross of lines that contain the single constructs. The advantage of this two-component system is that a wide array of tissue-specific expression patterns can be generated for a specific transgene, by simply crossing selected parent lines expressing the UAS-CCP construct with various tissue-specific GAL4-VP16 lines. A tissue-specific promoter/CCP combination that gives a desired phenotype can subsequently be recloned in a single expression vector, to avoid stacking of transgene constructs in commercial lines.

Primary transformants are characterized by Northern and Western blotting using 1-4 week old plantlets. Expression levels were compared with those of non-transformed (control) plants.

Example 4 Downregulation of Target CCP Genes in Transgenic Plants

Plant genes can be specifically downregulated by antisense and co-suppression technologies. These technologies are based on the synthesis of antisense transcripts, complementary to the mRNA of a given CCP gene. There are several methods described in literature, that increase the efficiency of this downregulation, for example to express the sense strand with introduced inverted repeats, rather than the antisense strand. The constructs for downregulation of target genes are made similarly as those for expression of recombinant proteins, i.e., they are fused to promoter sequences and transcription termination sequences (see example 3). Promoters used for this purpose are constitutive promoters as well as tissue-specific promoters.

Example 5 Agrobacterium-Mediated Rice Transformation

Mature dry seeds of the rice japonica cultivars Nipponbare or Taipei 309 are dehusked, sterilised and germinated on a medium containing 2,4-D (2,4-dichlorophenoxyacetic acid). After incubation in the dark for four weeks, embryogenic, scutellum-derived calli are excised and propagated on the same medium. Selected embryogenic calluses are then co-cultivated with Agrobacterium. Widely used Agrobacterium strains such as LBA4404 or C58 harbouring binary T-DNA vectors can be used. The hpt gene in combination with hygromycin is suitable as a selectable marker system but other systems can be used. Co-cultivated callus is grown on 2,4-D-containing medium for 4 to 5 weeks in the dark in the presence of a suitable concentration of the selective agent. During this period, rapidly growing resistant callus islands develop. After transfer of this material to a medium with a reduced concentration of 2,4-D and incubation in the light, the embryogenic potential is released and shoots develop in the next four to five weeks. Shoots are excised from the callus and incubated for one week on an auxin-containing medium from which they can be transferred to the soil. Hardened shoots are grown under high humidity and short days in a phytotron. Seeds can be harvested three to five months after transplanting. The method yields single locus transformants at a rate of over 50% (Aldemita and Hodges (1996) Planta 199:612-617; Chan et al. (1993) Plant Mol. Biol. 22: 491-506; Hiei et al. (1994) Plant J. 6:271-282).

Example 6 Expression of Recombinant CCP Proteins in Bacterial Cells

In this example, the CCP molecules of the present invention are expressed as a recombinant glutathione-S-transferase (GST) fusion polypeptide in E. coli and the fusion polypeptide is isolated and characterized. Specifically, CCP molecules are fused to GST and this fusion polypeptide is expressed in E. coli, e.g., strain PEB199. Expression of the GST-CCP fusion protein in PEB199 is induced with IPTG. The recombinant fusion polypeptide is purified from crude bacterial lysates of the induced PEB199 strain by affinity chromatography on glutathione beads. Using polyacrylamide gel electrophoretic analysis of the polypeptide purified from the bacterial lysates, the molecular weight of the resultant fusion polypeptide is determined.

Example 7 Expression of Recombinant CCP Proteins in COS Cells

To express the CCP gene of the present invention in COS cells, the pcDNA/Amp vector by Invitrogen Corporation (San Diego, Calif.) is used. This vector contains an SV40 origin of replication, an ampicillin resistance gene, an E. coli replication origin, a CMV promoter followed by a polylinker region, and an SV40 intron and polyadenylation site. A DNA fragment encoding the entire CCP protein and an HA tag (Wilson et al. (1984) Cell 37:767) or a FLAG tag fused in-frame to its 3′ end of the fragment is cloned into the polylinker region of the vector, thereby placing the expression of the recombinant protein under the control of the CMV promoter.

To construct the plasmid, the CCP DNA sequence is amplified by PCR using two primers. The 5′ primer contains the restriction site of interest followed by approximately twenty nucleotides of the CCP coding sequence starting from the initiation codon; the 3′ end sequence contains complementary sequences to the other restriction site of interest, a translation stop codon, the HA tag or FLAG tag and the last 20 nucleotides of the CCP coding sequence. The PCR amplified fragment and the pcDNA/Amp vector are digested with the appropriate restriction enzymes and the vector is dephosphorylated using the CIAP enzyme (New England Biolabs, Beverly, Mass.). Preferably the two restriction sites chosen are different so that the Kinase and/or Phosphatase gene is inserted in the correct orientation. The ligation mixture is transformed into E. coli cells (strains HB101, DH5a, SURE, available from Stratagene Cloning Systems, La Jolla, Calif., can be used), the transformed culture is plated on ampicillin media plates, and resistant colonies are selected. Plasmid DNA is isolated from transformants and examined by restriction analysis for the presence of the correct fragment.

COS cells are subsequently transfected with the CCP-pcDNA/Amp plasmid DNA using the calcium phosphate or calcium chloride co-precipitation methods, DEAE-dextran-mediated transfection, lipofection, or electroporation. Other suitable methods for transfecting host cells can be found in Sambrook, J., Fritsh, E. F., and Maniatis, T. Molecular Cloning: A Laboratory Manual. 2nd, ed., Cold Spring Harbor Laboratory, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1989. The expression of the CCP polypeptide is detected by radiolabelling (³⁵S-methionine or ³⁵S-cysteine available from NEN, Boston, Mass., can be used) and immunoprecipitation (Harlow, E. and Lane, D. Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1988) using an HA specific monoclonal antibody. Briefly, the cells are labelled for 8 hours with ³⁵S-methionine (or ³⁵S-cysteine). The culture media are then collected and the cells are lysed using detergents (RIPA buffer, 150 mM NaCl, 1% NP-40, 0.1% SDS, 0.5% DOC, 50 mM Tris, pH 7.5). Both the cell lysate and the culture media are precipitated with an HA specific monoclonal antibody. Precipitated polypeptides are then analyzed by SDS-PAGE.

Alternatively, DNA containing the Kinase and/or Phosphatase coding sequence is cloned directly into the polylinker of the pcDNA/Amp vector using the appropriate restriction sites. The resulting plasmid is transfected into COS cells in the manner described above, and the expression of the CCP polypeptide is detected by radiolabelling and immunoprecipitation using a CCP specific monoclonal antibody.

Example 8 In Vitro Phosphorylation of CDC2DN-IC26M by Plant CDKs

The CDC2bDN-IC26M coding region (SEQ ID NO:4) was amplified by PCR with Pfu polymerase (Stratagene, La Jolla, Calif.). The PCR product was subcloned into pET19b (Novagen, Madison, Wis.), to obtain CDC2bDN-IC26 MpET19b. The CDC2bDN-IC26M gene is located downstream of a T1lac promoter, in frame with a sequence encoding a 10-histidine tag followed by an enterokinase recognition site. Escherichia coli BL21(DE3) cells (Novagen) containing the CDC2bDN-IC26 MpET19b plasmid were grown at 37° C. in M9 medium (Sambrook and Russel, Molecular Cloning, A Laboratory Manual, 3^(rd) Edition, CSHL Press, CSH New York, 2001), supplemented with 100 μg/ml of ampicillin, to obtain a cell density corresponding to an A600 of 0.6. Subsequently, expression of the CDC2bDN-IC26M gene was induced by addition of 0.4 mM isopropyl β-D-thiogalactoside, and culture was continued for 4 h at 30° C.

Cells were collected in lysis buffer containing 50 mM sodium phosphate buffer, pH 8.0, 300 mM NaCl, 0.1% Triton X-100, and 1 mM phenylmethylsulfonyl fluoride (PMSF) and were lysed on ice by sonication. The extract was clarified by centrifugation for 20 minutes at 20,000×g. The crude extract was loaded at 4° C. on a nickel-nitrilotriacetic acid-agarose affinity resin (Qiagen), and protein fractionation was performed according to the manufacturer's instructions. The fractions containing the CDC2bDN-IC26M fusion protein were pooled.

CDC2bDN-IC26M kinase assays were performed with CDK complexes purified from total plant (Arabidopsis seedlings) protein extracts by p13^(suc1)-Sepharose affinity binding according to Azzi et al. (Eur. J. Biochem. 203: 353-360). Briefly, p13^(suc1) was purified from an overproducing E. coli strain by chromatography in Sephacryl S2000, and conjugated to CNBr-activated Sepharose 4B (Pharmacia) according to the manufacturer's instructions. Total plant protein extracts (300 μg) were incubated with 50 μl 50% (v/v) p13^(suc1)-Sepharose beads for 2 h at 4° C. The washed beads were combined with 30 μl kinase buffer containing ˜1 mg/ml CDC2bDN-IC26M, 150 mM ATP and 1 μCi of [-32P]ATP (Amersham). After 20 minutes of incubation at 30° C., samples were analysed by SDS-PAGE and autoradiographed.

As shown in FIG. 48, the purified CDC2bDN-IC26M protein is phosphorylated by CDKs in vitro.

Example 9 PCR Amplification of AtDPb

Based on available sequence data of putative plant DP-related partial clones from the databank (soybean DP(AI939068), tomato DP(AW217514), and cotton DP (AI731675)), three oligonucleotides, corresponding to the most conserved part of the DNA-binding and E2F heterodimerization domains (MKVCEKV, SEQ ID NO:240; LNVLMAMD, SEQ ID NO:241 and FNSTPFEL, SEQ ID NO:242), were synthesized and designated A (ATAGAATTCATGAAAGTTTGTGAAAAGGTG, SEQ ID NO:243), B (ATAGAATTCCTGAATGTTCTCATGGCAATGGAT, SEQ ID NO:244) and C (ATAGGATCCCAGCTCAAAAGGAGTGCTATTGAA, SEQ ID NO:245), respectively.

PCR was performed on an Arabidopsis/yeast two-hybrid suspension culture cDNA library. The PCR products were purified, digested with EcoRI and BamHI, and ligated into pCR-XL-TOPO vector (Invitrogen). The cloned inserts were sequenced by double-stranded dideoxy sequencing.

Example 10 Construction of AtDP and AtE2F Mutants, In Vitro Transcription-Translation System and Immunoprecipitation

Influenza hemagglutinin (HA)-tagged versions of the wild-type and mutant AtE2Fa and AtE2Fb were constructed by cloning into the pSK plasmid (Stratagene) containing the HA-tag (SEQ ID NO:202). The AtE2F mutants, namely AtE2Fa 1-420 (SEQ ID NO:217), AtE2Fa 162-485 (SEQ ID NO:218), and AtE2Fb 1-385 (SEQ ID NO:206), were obtained by PCR and cloned into the EcoRI and BamHI sites of HA-pSK. The c-myc (SEQ ID NO:200)-tagged versions of wild-type and AtDP mutants (AtDPa 1-292, SEQ ID NO:114; AtDPa 121-292, SEQ ID NO:211; AtDPa 1-142, SEQ ID NO:208; AtDPa 172-292, SEQ ID NO:213; AtDPa 121-213, SEQ ID NO:212; and AtDPb 1-385, SEQ ID NO:127; AtDPb 182-385, SEQ ID NO:216; AtDPb 1-263, SEQ ID NO:223; AtDPb 1-193, SEQ ID NO:214; and AtDPb 182-263, SEQ ID NO:215) were generated by PCR and cloned into the EcoRI and PstI sites of the pBluescript plasmid (Stratagene) containing a double c-myc tag. All cloning steps were carried out according to standard procedures, and the reading frames were verified by direct sequencing.

In vitro transcription and translation experiments were performed using the TNT T7-coupled wheat germ extract kit (Promega) primed with appropriate plasmids for 90 min at 30° C. For immunoprecipitation, 10 μl of the total in vitro translated extract (50 μl) was diluted at 1:5 in Nonidet P40 buffer (50 mM Tris, pH 7.4, 150 mM NaCl, 1% Nonidet P40, 1 mM phenylmethylsulfonyl fluoride, 10 μg/ml leupeptin/aprotinin/pepstatin) and incubated for 2 h at 4° C. with anti-c-myc (9E10; BabCo) or anti-HA (16B12; BabCo) antibodies. Protein-A-Sepharose (40 μl 25% (v/v)) was added and incubated for 1 h at 4° C., then the beads were washed four times with Nonidet P40 buffer. Immune complexes were eluted with 10 μl 2 U sodium dodecyl sulfate (SDS) sample buffer and analyzed by 10% or 15% SDS-PAGE and by autoradiography.

An overview of the AtDP and AtE2F fragments and their SEQ ID NOs is given in Table 4.

TABLE IV SEQ ID NO SEQ ID NO amino acid DNA CCP or partial CCP sequence sequence AtE2Fa 226-356 205 228 AtE2Fb 1-385 206 AtE2Fb 1-127 207 AtDPa 1-142 208 AtDPa 42-142 209 AtDPa 42-292 210 AtDPa 121-292 211 229 AtDPa 121-213 212 AtDPa 172-292 213 AtDPb 1-193 214 AtDPb 182-263 215 230 AtDPb 182-385 216 231 AtE2Fa 1-420 217 AtE2Fa 162-485 218 AtE2Fa 1-38 219 AtDPa 1-214 220 239 AtDPa 143-292 221 232 AtDPa 143-213 222 233 AtDPb 1-263 223 234 AtE2Fa 232-282 224 235 AtE2Fa 232-352 225 236 AtE2Fb 194-243 226 237 AtE2Fb 194-311 227 238

Example 11 In Vitro Interaction Between AtDPs, AtE2Fs and Mutants Thereof Illustrated by Immunoprecipitation Experiments

The AtDPa and AtDPb can efficiently interact in vitro with AtE2Fa and AtE2Fb. As a first step in comparing the biochemical properties of AtDPa and AtDPb, the ability of these molecules to heterodimerize with AtE2Fa and AtE2Fb was tested. For this purpose, the coupled in vitro transcription-translation system was used in which the c-myc-tagged AtDPa or AtDPb was co-expressed with the HA-tagged AtE2Fa or AtE2Fb. One part of each sample was resolved by SDS-PAGE (FIGS. 50 and 51, panels A), while another part was subjected to immunoprecipitation with monoclonal anti-c-myc antibodies (FIGS. 50 and 51, panels B). In the absence of DP proteins, no AtE2F2a or AtE2F2b was precipitated by the anti-c-myc antibodies (FIG. 51, panel B, lane 1). However, both HA-AtE2F proteins co-precipitated reproducibly with c-myc-tagged AtDPa (FIG. 50, panel B, lanes 1 and 2) and AtDPb (FIG. 51, panel B, lanes 3 and 4). Identical results were obtained in a reciprocal experiment with anti-HA monoclonal antibodies. These data revealed that both Arabidopsis DP-related proteins interacted in vitro with the different Arabidopsis E2F-related proteins.

The conserved dimerization domain of the AtE2Fs seemed to be important for the interaction with the AtDPs, because mutational analysis showed that deletion neither of the N-terminal extension nor the C-terminal part of AtE2Fa and AtE2Fb impaired the interaction with the DPs (FIGS. 50 and 51, panels B). Similar results were obtained by two-hybrid analysis (see Table 5 of Example 12). To test whether the structural requirements for heterodimerization of the AtDPs were similar to those of their animal homologs, several deletion mutants of AtDPa and AtDPb were constructed (for a schematic illustration, see FIGS. 52 and 53), tagged with the c-myc epitope (FIGS. 54 and 55, panels A). The interactions between the mutant AtDPs and AtE2Fb were analyzed in immunoprecipitation experiments with the specific anti-HA or anti-c-myc antibodies (Figures A6 and A7, panels B and C, respectively). As shown in FIGS. 54 and 55, mutant AtDP proteins with deleted DNA-binding domain could bind sufficiently to the co-translated HA-AtE2Fb proteins (FIG. 54, panel C, lane 2; and FIG. 55, panel C, lane 2). No detectable interaction was found between the AtE2Fb protein and mutant DP proteins containing the complete DNA-binding domain, but lacking the putative dimerization domain (FIG. 54, panel C, lane 3; FIG. 55, panel C, lane 4). Thus, the N-terminal part of both AtDP proteins, including the conserved DNA-binding domain, was not sufficient for the in vitro interaction to occur. In contrast, a mutant form of AtDPb (amino acids 1-263; SEQ ID NO:223) could bind to AtE2Fb (FIG. 55, panel C, lane 3), indicating that the region of AtDPb between amino acids 182 and 263 was required for interaction with AtE2Fb.

To confirm this hypothesis, a deletion mutant of AtDPb (182-263, SEQ ID NO:215) was constructed and, as expected, it could bind to AtE2Fb (FIG. 56). The requirement for the homologous dimerization domain of AtDPa for the interaction with AtE2Fb was supported by a binding assay in which the mutant AtDPa 172-292 (SEQ ID NO:213), with the N-terminal part of the dimerization domain deleted, failed to bind to AtE2Fb (FIG. 54, panels B and C, lanes 4). However, when the E2F-binding activity of the predicted dimerization domain of the AtDPa (amino acid positions 121-213, SEQ ID NO:212) was tested, no interaction could be detected between this region and the AtE2Fb protein (FIG. 54, panel B, lane 5). These data indicate that other carboxyl-terminal regions of AtDPa are required for the stable interaction with AtE2Fb.

Example 12 Yeast Two-Hybrid Experiments for Showing Interaction Between DP and E2F Mutants

For library screening, vectors and strains (HF7c) were provided with the Matchmaker two-hybrid system (Clontech). The dimerization and DNA-binding domains of the AtE2Fa (amino acids 226-356; SEQ ID NO:205) were amplified by polymerase chain reaction (PCR) and subcloned in-frame with the GAL4 DNA-binding domain of pGBT9 (Clontech) to create the bait plasmid pGBTE2Fa226-356. Screens were performed as described previously (De Veylder et al. 1999; Planta 208, 453-462). A second library screening was performed with the AtE2Fb construct (pGBTE2Fb-Rb) lacking the Rb-binding domain (amino acids 1-385; SEQ ID NO:206). Plasmids from interacting clones were isolated and sequenced.

For the yeast two-hybrid interaction experiments, a number of yeast two-hybrid prey (in pAD-GAL424) plasmids were created by PCR amplification of fragments from the AtDPa (DPa 1-292, SEQ ID NO:114; DPa 1-142, SEQ ID NO:208; DPa 42-142, SEQ ID NO:209; DPa 42-292, SEQ ID NO:210; DPa 121-292, SEQ ID NO:211; DPa 121-213, SEQ ID NO:212; and DPa 172-292, SEQ ID NO:213) and AtDPb (DPb 1-385, SEQ ID NO:127; DPb 1-193, SEQ ID NO:214; DPb 182-263, SEQ ID NO:215; and DPb 182-385, SEQ ID NO:216) genes and confirmed by sequencing. Different combinations between bait (pGBTE2Fa226-356, pGBTE2Fb-Rb, or pGBTE2Fb 1-127, SEQ ID NO:207) and prey constructs were transformed into yeast cells and assayed for their ability to grow on His⁻ minimal media after 3 days of incubation at 30° C. Bait plasmids co-transformed with empty pAD-GAL424 and prey plasmids co-transformed with empty pGBT9 were assessed along as controls for the specificity of the interaction.

An overview of the AtDP and AtE2F fragments and their SEQ ID NOs is given in Table 4.

The results obtained were confirmed by two-hybrid interaction analysis. pGBTE2Fa226-356 and pGBTE2Fb-Rb were co-transformed in an appropriate yeast reporter stain with a plasmid producing the full-length AtDPa or AtDPb protein fused to the GAL4 transactivation domain. The specific reconstitution of GAL4-dependent gene expression measured as the ability to grow in the absence of histidine confirms the interaction between the two DP and E2F proteins (Table 5).

TABLE V AtDPs and AtE2Fs interaction in yeast two-hybrid assays. Preys DPa DPa DPa DPa DPa DPa DPa DPb DPb DPb DPb E2Fa pAD- Baits 1-292 1-142 42-142 42-292 121-292 121-213 172-292 1-385 1-193 182-263 182-385 226-356 GAL424 pGBT + − − + + − − + − + + − − E2Fa 226-356 pGBT + − − + + − − + − + + − − E2Fb- Rb pGBT − NT NT NT NT NT NT − NT NT NT − − E2Fb 1-127 pGBT − NT NT NT NT NT NT − NT NT NT + − DPa 1-292 pGBT NT NT NT NT NT NT NT − NT NT NT + − DPb 1-385 pBGT9 − − − − − − − − − − − − − Different combinations between AtE2Fs bait and AtDPs prey constructs were tested for growth on His⁻ minimal media. −, no interaction; +, positive interaction; NT, not tested.

Example 13 RNA Isolation and Reverse Transcription-(RT)-PCR analysis of AtDP and AtE2F Expression

A. thaliana (L.) Heynh. cell suspension cultures were maintained as described previously (Glab et al. 1994, FEBS Lett. 17, 207-211). The cells were partially synchronized by the consecutive addition of aphidicolin (5 μg/ml) and propyzamide (1.54 μg/ml). The aphidicolin block was left for 24 hours. The cells were washed for 1 hour in B5 medium before the addition of propyzamide. Samples were taken at the end of the 24 hour aphidicolin block, at the end of a 1 hour washing step, and at 1, 2, 3, and 4 hours after the addition of propyzamide to the culture medium. Total RNA was isolated from the Arabidopsis cell suspension culture according to Magyar et al. (1997), Plant Cell 9, 223-235, and with the Triazol reagent (Gibco/BRL) from different organs. Semi-quantitative RT-PCR amplification was carried out on reverse-transcribed mRNA, ensuring that the amount of amplified product stayed in linear proportion to the initial template present in the reaction. 10 μl from the PCR was transferred onto Hybond-N/membrane, hybridized to fluorescein-labeled gene-specific probes (Gene-Images random prime labeling module; Amersham Pharmacia Bio-tech), detected with the CDP-Star detection module (Amersham), and visualized by short exposure to Kodak X-OMAT autoradiography film.

The following primer pairs (forward and reverse) were used for the amplification: 5′-ATAGAATTCATGTCCGGTGTCGTACGA-3′ (SEQ ID NO:249, EcoRI site underlined) and 5′-ATAGGATCCCACCTCCAATCTTTCTGCAGC-3′ (SEQ ID NO:250, BamHI site underlined) for AtE2Fa (GenBank accession number AJ294533); 5′-ATAGAATTCGAGAAGAAAGGGCAAT CAAGA-3′ (SEQ ID NO:251, EcoRI site underlined) and 5′-ATACTGCAGAGAAATCTCGATTTCGACTAC-3′ (SEQ ID NO:252, PstI site underlined) for AtDPa (GenBank accession number AJ294531); 5′-GCCACTCTCATAGGGTTCTC CATCG-3′ (SEQ ID NO:253) and 5′-GGCATGCCTCCAAGATCCTTGAAGT-3′ (SEQ ID NO:254) for Arath;CDKA;1 (Genbank accession number X57839); 5′-GGGTCTTGGTCGTTTTACTGTT-3′ (SEQ ID NO:255) and 5′-CCAAGACGATGACAACAGATACAGC-3′ (SEQ ID NO:256) for Arath;CDKB1;1 (Genbank accession number X57840); 5′-ATAAACTAAATCTTCGCTGAA-3′ (SEQ ID NO:257) and 5′-CAAACGCGGATCTGAAAAACT-3′ (SEQ ID NO:258) for histone 114 (Genbank accession number M17132); 5′-TCTCTCTTCCAAATCTCC-3′ (SEQ ID NO:259) and 5′-AAGTCTCT CACTTTCTCACT-3′ (SEQ ID NO:260) for R005 (AtCYP1, GenBank accession number U072676) (Chou and Gasser 1997, Plant Mol. Biol. 35, 873-892); 5′-CTAAGCTCTCAAGATCAAAGGCTTA-3′ (SEQ ID NO:261) and 5′-TTAACATTG CAAAGAGTTTCAAGGT-3′ (SEQ ID NO:262) for actin 2 gene (GenBank accession number U41998) (An et al. 1996, Plant J. 10, 107-121).

Example 14 The AtDPa and the AtE2Fa Genes are Co-Expressed in a Cell Cycle Phase-Dependent Manner

The identification of the AtDPa in a yeast two-hybrid screen as a gene encoding an AtE2Fa-associating protein indicated that it might act cooperatively in the plant cells as a functional heterodimer. To strengthen this hypothesis, we investigated whether both genes were co-regulated at the transcriptional level. Tissue-specific expression analysis revealed that both genes were clearly up-regulated in flowers and were very strongly transcribed in actively dividing cell suspension cultures (FIG. 57). Expression in these tissues could be a sign for the correlation between the actual proliferation activity of a given tissue and the transcript accumulation, as can be seen from the Arath;CDKB1;1 gene. AtDPa transcripts were also detectable in leaf and, to a lesser extent, in root and stem tissues, whereas AtE2Fa transcripts were virtually undetectable in roots and stem with only slight levels of expression in leaf tissues. Cell cycle phase-dependent gene transcription was studied using an Arabidopsis cell suspension that was partially synchronized by the sequential treatment with aphidicolin and propyzamide. The Arabidopsis histone H4 and the Arath;CDKB1;1 gene were included to monitor the cell cycle progression (FIG. 58) (Chaubet et al. 1996, Plant J. 10, 425-435; Segers et al. 1996, Plant J. 10, 601-612). Bearing in mind the partial synchronization of the culture, it can be observed that histone H4 transcript levels peaked immediately after the removal of the inhibitor and decrease gradually thereafter (FIG. 58). The opposite expression pattern could be observed for the Arath;CDKB1;1 gene, illustrating that cells entered the G2-M phases with partial synchrony. Within this experimental setting, the AtDPa and the AtE2Fa genes show a very similar expression pattern. Both exhibit higher transcript accumulation before the peak of histone H4 gene expression and quickly decay in the following samples (FIG. 58). The similarity in the expression patterns of Arabidopsis AtDPa and AtE2Fa supports the possibility that they act cooperatively as a heterodimer during the S phase.

Example 15 Transformation of Arabidopsis Thaliana with CaMV35S::DPa

Arabidopsis plants were transformed (using the in planta flower dip method; Clough and Bent, Plant J. 16:735-743, 1998) with a construct containing the DPa gene under the control of the CaMV ³⁵S promoter. The lines were molecularly analysed by northern blotting. As can be seen in FIG. 59, all lines showed increased DPa levels in comparison with the untransformed control. Generally, two classes of lines were observed: weakly expressing (e.g., 16) and strongly expressing (e.g., 23) lines (see FIG. 59). The plants are subsequently analyzed for phenotypic alterations as described herein.

EQUIVALENTS

Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims. 

1. An isolated nucleic acid molecule selected from the group consisting of: (a) a nucleic acid molecule comprising the nucleotide sequence set forth in SEQ ID NO: 3, 6, 12, 13, 29, 41, 42, or 45; (b) a nucleic acid molecule which encodes a polypeptide comprising the amino acid sequence set forth in SEQ ID NO: 69, 72, 78, 79, 95, 108, or 111; (c) a nucleic acid molecule which encodes a naturally occurring allelic variant of a polypeptide comprising the amino acid sequence set forth in SEQ ID NOs: 69, 72, 78, 79, 95, 108, or 111; (d) a nucleic acid molecule comprising a nucleotide sequence which is at least 60% identical to the nucleotide sequence of SEQ ID NO: 3, 6, 12, 13, 29, 41, 42, or 45, or a complement thereof; (e) a nucleic acid molecule comprising a fragment of at least 50 nucleotides of a nucleic acid comprising the nucleotide sequence of SEQ ID NO: 3, 6, 12, 13, 29, 41, 42, or 45, or a complement thereof; (f) a nucleic acid molecule which encodes a polypeptide comprising an amino acid sequence at least about 60% identical to the amino acid sequence of SEQ ID NO: 69, 72, 78, 79, 95, 108, or 111; and (g) a nucleic acid molecule which encodes a fragment of a polypeptide comprising the amino acid sequence of SEQ ID NO: 69, 72, 78, 79, 95, 108, or 111, wherein the fragment comprises at least 15 contiguous amino acid residues of the amino acid sequence of SEQ ID NO: 69, 72, 78, 79, 95, 108, or
 111. 2-4. (canceled)
 5. An isolated nucleic acid molecule which hybridizes to the nucleic acid molecule of claim 1, under stringent conditions.
 6. An isolated nucleic acid molecule comprising a nucleotide sequence which is complementary to the nucleotide sequence of the nucleic acid molecule of claim
 1. 7. An isolated nucleic acid molecule comprising the nucleic acid molecule of claim 1, and a nucleotide sequence encoding a heterologous peptide.
 8. A vector comprising the nucleic acid molecule of claim
 1. 9. A cell comprising the nucleic acid molecule of claim
 1. 10. A host cell transfected with the vector of claim
 8. 11. A method of producing a polypeptide comprising culturing the host cell of claim 10 in an appropriate culture medium to, thereby, produce the polypeptide.
 12. An isolated polypeptide selected from the group consisting of: a) a fragment of a polypeptide comprising the amino acid sequence of SEQ ID NOs: 69, 72, 78, 79, 95, 108, or 11, wherein the fragment comprises at least 15 contiguous amino acids of SEQ ID NOs:69, 72, 78, 79, 95, 108, or 111; b) a naturally occurring allelic variant of a polypeptide comprising the amino acid sequence of SEQ ID NOs:69, 72, 78, 79, 95, 108, or 111, wherein the polypeptide is encoded by a nucleic acid molecule which hybridizes to a nucleic acid molecule consisting of SEQ ID NOs:3, 6, 12, 13, 29, 41, 42, or 45 under stringent conditions; c) a polypeptide which is encoded by a nucleic acid molecule comprising a nucleotide sequence which is at least 60% identical to a nucleic acid comprising the nucleotide sequence of SEQ ID NOs:3, 6, 12, 13, 29, 41, 42, or 45; and d) a polypeptide comprising an amino acid sequence which is at least 60% identical to the amino acid sequence of SEQ ID NOs:69, 72, 78, 79, 95, 108, or
 111. 13. The isolated polypeptide of claim 12 comprising the amino acid sequence of SEQ ID NOs:69, 72, 78, 79, 95, 108, or
 111. 14. The polypeptide of claim 12, further comprising one or more heterologous amino acid sequences.
 15. An antibody which selectively binds to a polypeptide of claim
 12. 16. A method for detecting the presence of a polypeptide of claim 12 in a sample comprising: a) contacting the sample with a compound which selectively binds to the polypeptide; and b) determining whether the compound binds to the polypeptide in the sample to thereby detect the presence of a polypeptide of claim 12 in the sample.
 17. The method of claim 16, wherein the compound which binds to the polypeptide is an antibody.
 18. A kit comprising a compound which selectively binds to a polypeptide of claim 12 and instructions for use.
 19. A method for detecting the presence of the nucleic acid molecule of claim 1 in a sample comprising: a) contacting the sample with a nucleic acid probe or primer which selectively hybridizes to the nucleic acid molecule; and b) determining whether the nucleic acid probe or primer binds to a nucleic acid molecule in the sample to thereby detect the presence of nucleic acid molecule of claim 1 in the sample.
 20. The method of claim 19, wherein the sample comprises mRNA molecules and is contacted with a nucleic acid probe.
 21. A kit comprising a compound which selectively hybridizes to a nucleic acid molecule of claim 1 and instructions for use.
 22. A method for identifying a compound which binds to the polypeptide of claim 12 comprising: a) contacting the polypeptide, or a cell expressing the polypeptide with a test compound; and b) determining whether the polypeptide binds to the test compound.
 23. The method of claim 22, wherein the binding of the test compound to the polypeptide is detected by a method selected from the group consisting of: a) detection of binding by direct detection of test compound/polypeptide binding; b) detection of binding using a competition binding assay; and c) detection of binding using an assay for CCP activity.
 24. A method for modulating the activity of a polypeptide of claim 12 comprising contacting the polypeptide or a cell expressing the polypeptide with a compound which binds to the polypeptide in a sufficient concentration to modulate the activity of the polypeptide.
 25. A method for identifying a compound which modulates the activity of a polypeptide of claim 12 comprising: a) contacting a polypeptide of claim 12 with a test compound; and b) determining the effect of the test compound on the activity of the polypeptide to thereby identify a compound which modulates the activity of the polypeptide.
 26. A transgenic plant comprising the nucleic acid molecule of claim
 1. 27. The transgenic plant of claim 26, wherein the plant is a monocot plant.
 28. The transgenic plant of claim 26, wherein the plant is a dicot plant.
 29. The transgenic plant of claim 26, wherein the plant is selected from the group consisting of Arabidopsis thaliana, rice, wheat, maize, tomato, oilseed rape, soybean, sunflower, and canola.
 30. A method for modulating the growth of a plant, comprising introducing into the plant a CCP modulator in an amount sufficient to modulate the growth of the plant, thereby modulating the growth of the plant.
 31. The method of claim 30, wherein the CCP modulator is a small molecule.
 32. The method of claim 30, wherein the CCP modulator is capable of modulating CCP polypeptide activity.
 33. The method of claim 32, wherein the CCP modulator is an anti-CCP antibody; or wherein the CCP modulator is a CCP polypeptide comprising the amino acid sequence of SEQ ID NOs: 67-132, 205, 211, 215-216 or 220-227, or a fragment thereof.
 34. (canceled)
 35. The method of claim 30, wherein the CCP modulator is capable of modulating CCP nucleic acid expression.
 36. The method of claim 35, wherein the CCP modulator is an antisense CCP nucleic acid molecule; wherein the CCP modulator is a ribozyme; or wherein the CCP modulator comprises the nucleotide sequence of SEQ ID NO: 1-66 or 228-239, or a fragment thereof. 37-38. (canceled)
 39. The method of claim 30, wherein the plant is a monocot plant.
 40. The method of claim 30, wherein the plant is a dicot plant.
 41. The method of claim 30, wherein the plant is selected from the group consisting of Arabidopsis thaliana, rice, wheat, maize, tomato, alfalfa, oilseed rape, soybean, sunflower, and canola.
 42. A method for modulating the cell cycle in a plant, comprising introducing into the plant a CCP modulator in an amount sufficient to modulate the cell cycle in the plant, thereby modulating the cell cycle in the plant.
 43. The method of claim 42, wherein the plant is a monocot plant.
 44. The method of claim 42, wherein the plant is a dicot plant.
 45. The method of claim 42, wherein the plant is selected from the group consisting of Arabidopsis thaliana, rice, wheat, maize, tomato, alfalfa, oilseed rape, soybean, sunflower, and canola 